You are given a mathematical function as follows, where all variables are of integer types. if s = 0 (A(s-1,A(s,t-1)). A(s, t)= t+1, A(s - 1,1), if s> 0 and t = 0 if s> 0 and t> 0 [4 points] (1) Give the C code for computing the function A(s, t) (2) Use comments to indicate the four steps of the Fantastic Four Abstract Approach. [2 points] (3) Write the main program to call your function and print the result. Your actual parameters are x and y. You must read the values of x and y from the keyboard. [2 points]