The Local Government Authority of Ghana wishes to computerize their activities. The Authority desires departments and units to be able to share files whiles it reduces some unnecessary cost. As the Head of IT unit your Head of Department has tasked you to research what connection type would be appropriate for LGA and why? As a tough headed Boss he requires that you give Three (3) key points to support your choice for and against?

a. productCost = 100

b. productPrice = productCost

c. productPrice = productName

d. productPrice = “24.95”

e. 15.67 = productCost

f. productCost = $1, 345.52

g. product Cost = productPrice − 10

h. productName = “mouse pad”

i. productCost + 20 = productPrice

j. productName = 3-inch nails

k. productName = 43

l. productName = “44”

m.“99” = productName

Answer:

(a) valid

(b) valid

(c) invalid

(d) valid

(e) invalid

(f) invalid

(g) invalid

(h) valid

(i) invalid

(j) invalid

(k) invalid

(l) valid

(m) invalid

Explanation:

(a) valid. Since productCost is a numerical variable, a value of 100 can be assigned to it.

(b) valid. Both productCost and productPrice are numerical variables and as such value of one can be stored in the other.

(c) invalid. productName is a string variable and cannot be directly assigned to productPrice which is a numeric variable.

(d) valid. productPrice is a numeric variable and 24.95 can be assigned to it.

(e) invalid. 15.67 is not a variable name and as such cannot have values assigned to it.

(f) invalid. $ and , are not numeric digits and as such cannot be assigned to productCost which is numeric.

(g) invalid. There should be no space between product and Cost. It should be productCost and not product Cost.

(h) valid. "mouse pad" is a string literal and can be assigned to productName which is a string variable.

(i) invalid. productCost + 20 is not a variable .

(j) invalid. 3-inch nails should be in quotes for it to be assignable to productName.

(k) invalid. 43 is a numeric literal and cannot be directly assigned to productName which is a string variable. In other words, 43 should be in quotes for it to be assignable to productName.

(l) valid. 44 (in quotes) is a string literal and can be assigned to productName which is a string variable.

(m) invalid. "99" is not a variable name and cannot hold or be assigned any value.

Answer:

a. True

Explanation:

The statement that a pen testing method or penetration test in which a tester who has a means of entry to an application behind its firewall imitates an attack that could be caused by a malicious insider.

A penetration test, which is also refer to as a pen test, pentest or ethical hacking, is an approved simulated cyberattack done on a computer system, performed in order to evaluate the security of the system. The test is carried out to identify both weaknesses or vulnerabilities including the potential for unauthorized parties to penetrate to the system's features and data.

The main purpose of performing this test is to identify any vulnerability in a system's defenses which attackers may take advantage of.

Answer:

A honeypot is a computer network set up to act as a decoy to track, deflect, or research trying to obtain unwanted access to the information system.

Explanation:

A honeypot is a device or device network designed to imitate possible cyber-attack targets. It can be utilized to detect or deflect assaults from a legitimate military target. It may also be used to collect knowledge on how cybercrime works.

Advantage:-

Disadvantage:-  

That honeypot doesn't replace any safety mechanisms; they just operate with your overall security infrastructure and improve it.

Answer:

I am writing a Python program:

This is the find_max_sales

def find_max_sales(tuple_list): #method that takes a list of tuples as parameter and returns the movie name which had the most sales

   maximum=0  #stores the maximum of the ticket sales

   name=""  #stores the name of the movie with maximum sales

   for tuple in tuple_list:  # iterates through each tuple of the tuple list

       [movie, sale]= tuple  #tuple has two items i.e. movie contains name of the movies and sale holds the total ticket sale of the movie

       if sale>maximum:  #if the sale value of a tuple is greater than that of maximum sale value

           maximum=sale  #assigns the maximum of sales to maximum variable

           name=movie  # assigns the movie name which had most sales to name variable

   return name #returns the movie name that had the most sales and not the full tuple

#Below is the list of list of movies. This list is passed to the find_max_sales method which returns the movies name from the list that had the most sales.

movie_list = [("Finding Dory", 486), ("Captain America: Civil War", 408), ("Deadpool", 363), ("Zootopia", 341), ("Rogue One", 529), ("The Secret Life of Pets", 368), ("Batman v Superman", 330), ("Sing", 268), ("Squad", 325), ("The Jungle Book", 364)]

print(find_max_sales(movie_list))

Explanation:

The program has a method find_max_sales that has one parameter tuple_list which is a list of tuples. Each tuple i.e. tuple has two items a movie which is a string and sale which is an integer. The movie represents the name of a movie, and the sales represents that movie's total ticket sales  The function has a loop that iterates through each tuple tuple of the list tuple_list. Variable maximum holds the value of the maximum sales. The if condition checks if the value of tuple sale is greater than that stored in maximum, at each iteration. If the condition evaluates to true then that sale tuple value is assigned to maximum variable so that the maximum holds the maximum of the ticket sales. The name variable holds the name of the movie corresponding to the maximum sale tuple value. The method returns the movie name from the tuple_list that has the most sales.

For example in the above given movie_list , the maximum of sale is of the movie Rogue One. When the method is called it returns the movie name and not the full tuple so the output of the above program is:

Rogue One

Answer:

a. Remove the affected servers from the network.

Explanation:

An organization's incident response process (IRP) can be defined as all of the process involved in the cleanup and recovery of data when they fall victim to an attack or cybersecurity breach. The incident response process comprises of six (6) important stages and these are;

1. Preparation.

2. Detection and analysis (identification).

3. Containment.

4. Eradication.

5. Recovery.

6. Review of incident activities.

When an organization's IRP prioritizes containment over eradication and an incident is discovered, where an attacker outside the organization installed a crypto-currency mining software on the organization's web servers. Given the organization's stated priorities, the cybersecurity engineer should remove the affected servers from the network.

A containment process is focused on taking steps to eliminate or contain the attack. It basically involves acting swiftly in response to the attack, so as to prevent it from spreading across board or in order to mitigate the damage already caused.

In this context, the cybersecurity engineer should remove the affected servers from the network in accordance with the organization's IRP priority (containment).

Furthermore, he could take a step further to contain the attack by installing a firewall and updating their policies in the Intrusion Prevention System (IPS) of the organization.

Answer:

To determine if the program solves the original problem

Explanation:

Required

Essence of validating a program

From list of given options, only the above option best describes the given illustration.

When a program is validated, it means that the results of the program are tested to meet the requirements of the user;

For a program to be validated, it means it has passed the stage of error checking and correction; whether syntax or run time errors;

However, when modifications are made, the program will need to be re-validated to ensure that it comports with its requirements.

Answer:

Any element that has a starting tag and doesn't have a closing tag is called a empty element.

:)

Answer:

This program is written using Java programming language.

No comments were used; however, see explanation section for line by line explanation

import java.util.*;

public class Nums {

   public static void main(String args[]) {

     Scanner input = new Scanner(System.in);

     System.out.println("1.");

     int userNum;

     System.out.print("Enter Integer: ");

     userNum = input.nextInt();

     System.out.println("You entered: "+userNum);

     System.out.println("2.");

     System.out.print("Enter Integer: ");

     userNum = input.nextInt();

     System.out.println("You entered: "+userNum);

     System.out.println(userNum+" squared is "+(userNum * userNum));

     System.out.println("And "+userNum+" cubed is "+(userNum * userNum * userNum)+"!!");

     System.out.println("3.");

     System.out.print("Enter Another integer: ");

     int userNum2 = input.nextInt();

     System.out.println(userNum+" + "+userNum2+" is "+(userNum + userNum2));

     System.out.println(userNum+" * "+userNum2+" is "+(userNum * userNum2));

   }

}

Explanation:

This enables the program accept inputs

     Scanner input = new Scanner(System.in);

This signifies the beginning of number 1

     System.out.println("1.");

Variable userNum is declared as type integer

     int userNum;

The line prompts the user for input

     System.out.print("Enter Integer: ");

The line accepts the input

     userNum = input.nextInt();

This line displays user input

     System.out.println("You entered: "+userNum);

This signifies the beginning of number 2

     System.out.println("2.");

This line prompts the user for input

     System.out.print("Enter Integer: ");

This line accepts input

     userNum = input.nextInt();

This line prints user input (as required in number 2)

     System.out.println("You entered: "+userNum);

This line calculates and prints the square of user input

     System.out.println(userNum+" squared is "+(userNum * userNum));

This line calculates and prints the cube of user input

     System.out.println("And "+userNum+" cubed is "+(userNum * userNum * userNum)+"!!");

This signifies the beginning of number 3

     System.out.println("3.");

This line prompts the user for another integer value

     System.out.print("Enter Another integer: ");

This line accepts the input from the user

     int userNum2 = input.nextInt();

This line adds the two inputs by the user and displays the result

     System.out.println(userNum+" + "+userNum2+" is "+(userNum + userNum2));

This line multiplies the two inputs by the user and displays the result

     System.out.println(userNum+" * "+userNum2+" is "+(userNum * userNum2));

Answer:

the floating-point instructions  should be run 1.5 times faster in order to execute entire program 1.25 times faster

Explanation:

Given that:

a program consists of integer and floating-point instructions. 60% of the total execution time is spent on floating point instructions and the remaining 40% is on integer instructions.

Let the integer be the total execution time = V

The  floating-point instructions = 60%

The integer instruction = 40%

The time spent on the floating-point instruction = 60/100 × V

= 0.6 V

The time spent on t he integer instruction = 40/100 × V

= 0.4 V

However; How much faster should we run the floating-point instructions to execute entire program 1.25 times faster

If we are to execute the entire program 1,25 times faster;

The new execution time = V/1.25

Assuming the new time spent on floating-point instruction = W

∵

W + 0.4 V = V/1.25

W = V/1.25 - 0.4 V

W = (V - 0.5V)/1.25

W = 0.4V

the new time spent on floating-point instruction = W = 0.4 V

The speed required to make the floating -point instruction to run faster = 0.6V/.4 V

= 1.5

Hence,  the floating-point instructions  should be run 1.5 times faster in order to execute entire program 1.25 times faster

Answer: A. Consult data disposition policies in the contract

Explanation:

This is a Government Contract and as such may be subject to certain restrictions on how information should be handled or even destroyed.

The first thing the company should do therefore is to check the Data Disposition Policies that were included in the contract to see if and how they are to destroy the data and then proceed from there.

Answer:

I am writing a Python program:

print("Tip Calculator \n")

bill = float(input("Cost of meal: "))

tip15pc = bill * 0.15

tip20pc = bill * 0.20

tip25pc = bill * 0.25

print("\n15%")

print("Tip amount: %.2f"% (tip15pc))

print("Total amount: %.2f \n" % (bill + tip15pc))

print("20%")

print("Tip amount: %.2f"% (tip20pc))

print("Total amount: %.2f \n" % (bill + tip20pc))

print("25%")

print("Tip amount: %.2f"% (tip25pc))

print("Total amount: %.2f" % (bill + tip25pc))

Explanation:

The program first prints the message: Tip Calculator

bill = float(input("Cost of meal: ")) This statement prompts the user to enter the amount of the bill of meal. The input value is taken as decimal/floating point number from user.

tip15pc = bill * 0.15  This statement calculates the cost of tipping at 15%

tip20pc = bill * 0.20 This statement calculates the cost of tipping at 20%

tip25pc = bill * 0.25 This statement calculates the cost of tipping at 25%

print("\n15%")  This statement prints the message 15%

print("Tip amount: %.2f"% (tip15pc))  this statement displays the amount of tip at 15% and the value is displayed up to 2 decimal places as specified by %.2f

print("Total amount: %.2f \n" % (bill + tip15pc))  This statement prints the total amount by adding the cost of mean with the 15% tip amount.

The program further computes the the amount of tip at 20% and 25%. The resultant values are displayed up to 2 decimal places as specified by %.2f Then the program prints the total amount by adding the cost of mean with the 20%  and 25% tip amounts just as computed for the 15% tip.

The screenshot of the program as well as its output is attached.

Answer:

vowels = ("a", "e", "i", "o", "u")

word = input("Enter a word: ")

is_all = True

for c in vowels:

   if c not in word:

       is_all = False

if is_all == True:

   print(word + " is a vowel word.")

else:

   print(word + " is not a vowel word.")

Explanation:

Initialize a tuple, vowels, containing every vowel

Ask the user to enter a word

Initially, set the is_all as True. This will be used to check, if every vowel is in word or not.

Create a for loop that iterates through the vowels. Inside the loop, check if each vowel is in the word or not. If one of the vowel is not in the vowels, set the is_all as False.

When the loop is done, check the is_all. If it is True, the word is a vowel word. Otherwise, it is not a vowel word.

Answer:

The answer is "Option B".

Explanation:

The Baseline measurement is an essential characteristic of effective coal company monitoring programs to assess the degree of mining effects and keep on improving effect monitoring the system will continue to be modified via periodical analyses, and the wrong choices can be defined as follows:

Answer:

Assuming that D is correct, the other answer is C.

Explanation:

I used Dell Support to confirm this.

It states that if the lights are off, it is not detecting the network and no connection is in place. You would want to confirm the NIC is enabled in the BIOS (as C states).

I hope this helps!

Answer:

The statement in python is as follows:

to_the_power_of(cube_side,3)

Explanation:

As stated as the requirement of the code segment, the statement takes as parameters a variable cube_side and a constant 3.

It then returns the volume of the cube; i.e. cube raise to power 3

See full program below

def to_the_power_of(val,powe):

    result = val**powe

    print(result)

cube_side = float(input("Cube side: "))

to_the_power_of(cube_side,3)

Explanation:

Without it, we may have endured convoluted keyboard commands for years, greatly hindering the process of bringing the PC into homes everywhere. The mouse revolutionized computer interfaces, simplified an otherwise scary machine, and helped connect the world.

Answer: Variants

Customize

Explanation:

Answer:

Variants and customize, I took the quiz just now

Explanation:

Answer:

The factors to consider when building a solution for optical workflow for car accident are the type of claim to be modelled, also to examine the level of automation in vehicles.

Some of the software solutions that meet the requirements are the A1 Tracker  which is very effective to the enterprise business and small business working with insurance. we also have the Mutual expert, Ninja Quote.

Explanation:

Solution

In suggesting an optical workflow for the car accident claim process it is of importance to understand the following factors such as, the type of claim to be modelled, it will be determined by the policy that the clients have for their cars. this will assist in classifying the workflow and giving a clear path of the design.

The number of expected claims is also a very important factor that should be added in the design. Another important factor to examine  the level of automation of the vehicles, this can be very useful in collecting the accident data in a more efficient way and also making it simple to design the model.

Presently there are several workflow softwares in the insurance that have encouraged a great deal and have made the workflow in the insurance companies more greater.

Some of the soft wares are the A1 Tracker  which are very effective and efficient in are highly applicable to the enterprise business and small business working with insurance, the software is convenient in monitoring the work progress in the company.

The other soft wares that have been quite useful in the industry for example the Insly, ISI enterprise, Mutual expert, Ninja Quoter among others. These software are some of the best soft wares available in the market that have met the workflow requirement in the insurance sector.

Answer:

(a). as the combination of IP address and port number to allow an application within a computer to set up a connection with another application in another computer without ambiguity.

Explanation:

The explanation is in the answer.

Question:

"The correct syntax for passing an array as an argument to a method when a method is called and an array is passed to it is: "

A) a[0]..a[a.length]

B) a()

C) a

D) a[]  

Answer:

The correct answer is A.

An example is given in the attachment.

Cheers!

Answer:

Following is the program in the python language

s="Hellooo" #string initialization

k=0 # variable declaration

vowel_count=0 #variable declaration

while k<len(s): #iterating the loop

   c1=s[k] #store in the c1 variable  

   if c1=='a' or c1=='e' or c1=='i' or c1=='o' or c1=='u': #check the condition

       vowel_count= vowel_count +1; # increment the variable vowel_count  

   k = k+1

print(vowel_count) #display

Output:

4

Explanation:

Following is the description of program

Answer:

public class ArithmeticMethods

{

public static void main(String[] args) {

    int number1 = 7;

    int number2 = 28;

 displayNumberPlus10(number1);

 displayNumberPlus10(number2);

 displayNumberPlus100(number1);

 displayNumberPlus100(number2);

 displayNumberPlus1000(number1);

 displayNumberPlus1000(number2);

}

public static void displayNumberPlus10(int number){

    System.out.println(number + 10);

}

public static void displayNumberPlus100(int number){

    System.out.println(number + 100);

}

public static void displayNumberPlus1000(int number){

    System.out.println(number + 1000);

}

}

Explanation:

Inside the main:

Initialize two integers, number1 and number2

Call the methods with each integer

Create a method called displayNumberPlus10() that displays the sum of the given number and 10

Create a method called displayNumberPlus100() that displays the sum of the given number and 100

Create a method called displayNumberPlus1000() that displays the sum of the given number and 1000

Answer:

I am writing a Python program:

def string_type(string):

   if string=="":  //if the string is empty

       return "empty"

   elif string.count(".")>1:  #if the period sign occurs more than once in string

       if string.count("\n"):  #checks if the new line occurs in the string

           return "page"  #if both the above cases are true then its a page

       return "paragraph"  # if the period sign condition is true then its a para

   elif string.count(" ")>=1:  #if no of spaces in string occur more than once

       return "sentence"  #returns sentence

   elif len(string)==1:  # if length of the string is 1 this

       return "character"  #returns character

   else:  #if none of the above conditions is true then its a word

       return "word" #returns word

Explanation:

def string_type(string):  this is the definition of method string_type which takes a string as argument and determines whether the type of string is a word, paragraph, page, sentence or empty.

if string=="" this if condition checks if the string is empty. If this condition is true then the method returns "empty"

elif string.count(".")>1  This condition checks if the string type is a paragragh

string.count(".")>1   and if string.count("\n") both statements check if the string type is a page.

Here the count() method is used which is used to return the number of times a specified string or character appears in the given string.

Suppose the string is "Paragraphs need to have multiple sentences. It's true.\n However, two is enough. Yes, two sentences can make a paragraph."

The if condition first checks if count(".")>1 which means it counts the occurrence of period i.e. "." in the string. If the period occurs more than once this means it could be a page. But it could also be a paragraph so in order to determine the correct string type another if statement if string.count("\n") inside elif statement determines if the string is a page or not. This statement checks the number of times a new line appears in the string. So this distinguishes the string type paragraph from string type page.

elif string.count(" ")>=1: statement determines if the string is a sentence. For example if the string is "i love to eat apples." count() method counts the number of times " " space appears in the string. If the space appears more than once this means this cannot be a single word or a character and it has more than one words. So this means its a sentence.

  elif len(string)==1:  this else if condition checks the length of the string. If the length of the string is 1 this means the string only has a single character. Suppose string is "!" Then the len (string) = 1 as it only contains exclamation mark character. So the method returns "character" . If none of the above if and elif conditions evaluates to true then this means the string type is a word.

Answer:

def string_type(string):

  if string=="":  //if the string is empty

      return "empty"

  elif string.count(".")>1:  #if the period sign occurs more than once in string

      if string.count("\n"):  #checks if the new line occurs in the string

          return "page"  #if both the above cases are true then its a page

      return "paragraph"  # if the period sign condition is true then its a para

  elif string.count(" ")>=1:  #if no of spaces in string occur more than once

      return "sentence"  #returns sentence

Explanation:

Answer:

I am writing a Python function:

def is_maxheap(list):

   #finds the length of the list  

   size=len(list)

   #loop has a variable i which starts traversing from root til end of last #internal node

   for i in range(int((size - 2) / 2) + 1):  

       if list[2 * i + 1] > list[i]:  #If left child is greater than its parent then return #false  

               return False  

       if (2 * i + 2 < size and

           list[2 * i + 2] > list[i]):    #checks if right child is greater, if yes then #returns false  

               return False

   return True

Explanation:

The function is_maxheap() traverses through all the internal nodes of the list iteratively. While traversing it checks if the  node is greater than its children or not. To check the working of this function you can write a main() function to check the working on a given list. The main() function has a list of integers. It then calls is_maxheap() method by passing that list to the function. The program displays a message: "valid max heap" if the list represents valid max-heap otherwise it returns invalid max heap.

def main():

   list = [10,7,8]  

   size = len(list)  

   if is_maxheap(list):

       print("Valid Max Heap")  

   else:  

       print("Invalid Max Heap")          

main()

The program along with its output is attached in a screenshot.

Answer:

[1] = 10

[2] = The same natural joins with their super entity set

[3] = Is in 3NF if R is in BCNF

[4] = Neither "1" or "2"

[5] = When changes in R.A are made

Explanation:

[1] The number of super keys of a relation R(A, B, C, D) with keys {A} and {B, C} is 10.  The super keys of the given relations are {A}; {A, B}; {A,C}; {A,D}; {A,B,C}; {A,B,D}; {A,C,D}; {A,B,C,D}; {B,C}; {B,C,D}.

[2] key is used to uniquely identify entity from entity set. So key for every entity is unique. Subentities can have different attributes. Also functional dependencies can be different but natural join with their super subsets will be same.

[3] For a relation R to be in BCNF it must be in 3NF but If a relation R is in 3NF it is not necessary that it will be in BCNF.

[4] The natural join of relations R and S is expressed by R ✕ S.

[5] If tuple constraint references an attribute R.A to S.B then every time a change is done in R.A the tuple constraint is checked.

Answer:

1. {(22, 22) (22, 23), (22, 24), (23, 22), (23, 23), (23, 24)} : Not reflective, Not symmetric, Not anti-symmetric, Transitive.

2.  {(21,21),(21,22),(22,21),(22,22),(23,23),(24,24)}: Reflective, symmetric.

Explanation:

Solution

Reflective: Of every element matched to its own element

Symmetric: For every (a,b) there should be (b,a)

Anti-symmetric: For every (a,b) there should not be (b,a)

Transitive: For every (a,b) ∈R and (b,c)∈ R -then (a,c) ER for all a, b, c ∈ A

Now,

1.{(22, 22) (22, 23), (22, 24), (23, 22), (23, 23), (23, 24)}

Not Reflective: This is because we don't have (21,21) (23,23) and (24,24)

Not symmetric: Because we don't have (23,24) and (24,23)

Not anti symmetric: We have both (22,23) and (23,22)

Transitive: It is either 22 or 23 be (a,b) and 24 (b,a)

2. {(21,21),(21,22),(22,21),(22,22),(23,23),(24,24)}

Reflective: For all we have (a,a)

Symmetric: For every (a,b) we have (b,a)

Not Anti-symmetric

Transitive

Answer:

a) struct GroceryItem{

string name;

float cost;  };

b) GroceryItem apple;

apple.name = "Granny Smith";

apple.cost = 0.79;

c) GroceryItem inventory[20];

d) inventory[5].name = "Cheese";

   inventory[10].cost = 3.50;

Explanation:

a) GroceryItem is the name of the structure and struct is a keyword which is used to create GroceryItem structure.

The structure has two members one is name of type string which means its holds the name strings of items. The other is cost which is a float type variable which supports floating point numbers and its holds the cost of item.

b) GroceryItem apple statement means that a variable apple is created which is of type GroceryItem

apple.name = "Granny Smith" This statement uses the apple to access the member variable name of GroceryItem  structure and sets the apples's name to Granny Smith.  The dot between apple variable and member variable name is basically used to access the member variable name of GroceryItem .  

apple.cost = 0.79; This statement uses the apple variable to access the member variable cost of GroceryItem  structure in order to set the apples's cost to 0.79.  The dot between apple variable and member variable cost is basically used to access the member variable cost of structure.

c) GroceryItem inventory[20];  This statement creates an array of GroceryItem structure. The array name is inventory and [20] is basically specifies the size of this array which is 20.

d) inventory[5].name = "Cheese";  This statement uses inventory array and access the name member of the structure GroceryItem to set the name of the 6th GroceryItem in inventory array to "Cheese". .Here [5] is the index of the 6th item of the inventory array as the array locations start from 0. So inventory[20] can contains 20 elements from 0 index to 19 index. So to set the name of 6th item 5th index is specified.

inventory[10].cost = 3.50;  This statement uses inventory array and access the cost member of the structure GroceryItem to set the cost of the 11th GroceryItem in inventory array to "3.50". Here [10] is the index of the 11th item of the inventory array as the array locations start from 0. So inventory[20] can contains 20 elements from 0 index to 19 index. So to set the cost of 11th item 10th index is specified

Answer:

c. a certificate.

Explanation:

Public key infrastructure authentication is intended to make transactions occurring through the internet as secure as possible. Public keys are usually assigned to entities like business firms or individuals, and digital certificates are given to them as proof that they have been authenticated.

A certificate authority has the role of signing, storing, and issuing digital certificates. A software or humans could be charged with the responsibility of actually ensuring a key to user binding if all conditions are satisfied.

Answer:

The mean  = 16

The standard deviation = 7.19

Explanation:

N1 = 200  X1 = 25   σ1 = 3

N2= 250  X2 = 10   σ2 = 4

N3 = 300  X3= 15   σ3 = 5

The mean of a combined distribution is given by:

[tex]X = \frac{X_1N_1+X_2N_2+X_3N_3}{N_1+N_2+N_3}\\X = \frac{25*200+10*250+15*300}{200+250+300}\\X=16[/tex]

The differences from the mean for each component are:

[tex]D_1 = 25-16=9\\D_2=10-16=-6\\D_3=15-16=-1[/tex]

The standard deviation of a combined distribution is given by:

[tex]\sigma=\sqrt{\frac{N_1(\sigma_1^2+D_1^2)+N_2(\sigma_2^2+D_2^2)+N_3(\sigma_3^2+D_3^2)}{N_1+N_2+N_3}}\\\sigma=\sqrt{\frac{200(3^2+9^2)+250(4^2+(-6)^2)+300(5^2+(-1)^2)}{200+250+300}}\\\sigma=\sqrt{\frac{18000+13000+7800}{750} }\\\sigma=7.19[/tex]

The mean  = 16

The standard deviation = 7.19