Exercise 11.A: create a C++ program that will calculate the area of a circle and prompt. The program should have the following functions: One function to collect a radius and return the radius. The radius must be between 1 and 20, otherwise, the program will ask the user to enter another radius. The function only returns a valid radius. One function to calculate the area of a circle. The formula to calculate the area of the circle is area = PI*radius2 Set PI as a global constant with value 3.1416. The radius is passed to the function as an argument. One function to prompt the result as” The area of a circle with radius ___ is _____ Exercise 11.B: create a C++ program that will prompt a random number between -10 and 10, inclusive. The program should have the following functions: One function that randomly generates and returns a number between -10 and 10, inclusive. One function that prompts the result as The random number is _______