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$*$radius$2$

Set PI as a global constant with value $3\mathrm{.}1416.$

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 $\_\_\_\_\_\_\_$