4. Consider the function IndexEqual(A,ij) that returns true if there exists an index x (i sx sj) such that A[x] = x; otherwise, returns false. You may assume A is a sorted integer array in which every element is unique. a. Write an efficient recursive algorithm for IndexEqual(1,1). b. What is the situation resulting in the best-case running time of your function, and give an expression for that running time? c. What is the situation resulting in the worst-case running time of your function, and give an expression for that running time in terms of n, where n=j-1+1