C programming!!!!! Expert onlyCompound interest. (a) Write a function to compute and return the amount of money, A, that you will have in n years if you invest P dollars now at annual interest rate i. Take n, i, and P as parameters. The formula is A = P(1 + i)n (b) Write a function to compute and return the amount of money, P, that you would need to invest now at annual interest rate i in order to have A dollars in n years. Take n, i, and A as parameters. The formula is:P =A / (1 + i)n (c) Write a function that will read and validate the inputs for this program. Using call by value/address, return an enumerated constant for the choice of formulas, a number of years, an interest rate, and an amount of money, in dollars. All three numbers must be greater than 0.0. (d) Write a main program that will call the input routine to gather the data. Then, depending on the user’s choice, it should call the appropriate calculation function and print the results of thecalculation.