I need a C++ program that uses the following recursive functions:

a. int bigDown(int x) that subtracts 1 from every digit of the given integer parameter that is 5 or larger

b. int even(int x) that deletes all odd digits from a positive integer parameter.

c. int useRecursion(int x) that returns the sum of the first two digits in a positive number. If there is only one digit, that digit is returned.