IN C Programming

Code and document the following functions using ITERATIVE and RECURSIVE functions (two implementations for each function: iteratively and recursively) Test the functions by calling them from a simple interactive main() function using a menu, with different values used to select the choice of function. Overall, you should have one C program (call it firstnameLastname_Lab1.c) containing one main() function and 10 other functions, where the functions are called based on the user input to the menu choices. The program should contain a loop that permits users to enter a new choice of function for each loop, until exit from the loop explicitly Factorial (0) = 1 ; 1 Factorial(n)n * (n-1)*...'2'1 Requirement: n >= 0; reject with error message otherwise Fibonacci(0)0; Fibonacci(1)1; Fibonacci(n) = Fibonacci(n-1) + Fibonacci(n-2); Requirement: n0; reject with error message otherwise gcd (x, y-x, if y-0 2 3 gcd (x, y) - gcd (y, x MOD y), if y>0 Requirement: x and y both 2 0; reject with error message otherwise Power(a,b)- ab Requirement: a > 0, b 0, b is an integer; reject with error message otherwise digProduct (x)-x if x