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Problem A: In mathematics, the notation $n!$ represents the factorial of the nonnegative integer $n$. The factorial of $n$ is the product of all the nonnegative integers from $1$ to $n$. For example, $$4! = 1 \cdot 2 \cdot 3 \cdot 4 \cdot = 24$$ and $$7! = 1 \cdot 2 \cdot 3 \cdot 4 \cdot 5 \cdot 6 \cdot 7 = 5040.$$ Write a program that lets the user enter a nonnegative integer then uses a loop to calculate the factorial of that number. Display the factorial.

Problem B: Write a program that calculates the amount of money a person would earn over a period of time if his or her salary is one penny the first day, two pennies the second day, and continues to double each day. The program should ask the user for the number of days. Display a table showing what the salary was for each day, then show the total pay at the end of the period. The output should be displayed in a dollar amount, not the number of pennies.

Problem C: Write a program that predicts the approximate size of a population of organisms. The application should use text boxes to allow the user to enter the starting number of organisms, the average daily population increase (as a percentage), and the number of days the organisms will be left to multiply. For example, assume the user enters the following values:
Starting number of organisms: 2
Average daily increase: 30%
Number of days to multiply: 10
The program should display the following table of data:
Day	Population
1	2
2	2.6
3	3.38
4	4.394
5	5.7122
6	7.42586
7	9.653619
8	12.5497
9	16.31462
10	21.209