Someone please help me with my computer science homework!

Write one single complete C++ program to do all sections below:

Part A:

I. Print "Please enter a positive 3-digit number: " and read in the number. If the number is not a positive 3-digit number, ask again until the number is valid.

II. Prints only the 3-digit numbers starting from the users input with 15 numbers (separated by spaces) on each line in a descending order.

Part B:

I. Print "Please enter an odd number between 9 to 19 (inclusive): " and read in the number. If the number is not within the range, ask again until the number is valid.

II. The program then prints out three big asterisks using the input value as the row height and column width for 1 big asterisk. There should be two spaces between the big asterisks.