Design a system in C++ that lets the user perform math operations (sum, difference, multiplication, division, average) on two numbers. The C++ program must be menu-driven, allowing the user to select an arithmetic operation from the list and input the numbers. Furthermore, your program must consist of the following functions: showChoice: This function shows the options to the user and explains how to enter data. Add: This function accepts two numbers as arguments and returns the sum. Subtract: This function accepts two numbers as arguments and returns their difference. Multiply: This function accepts two numbers as arguments and returns the product. Divide: This function accepts two numbers as arguments and returns a quotient. Average: This function accepts two numbers as arguments and returns their average.