Problem 1. (13 marks) On sorting lower bound. a. (5 marks) Consider the Searching problem which takes as input a sorted array A with n elements and a key k, and we return the largest element in A that is less than or equal to k. From Exercise I of Assignm ent #1, we know that it can be solved by binary-search in O(log n) time. Show that any algorithm for solving this Searching problem that accesses the array only via comparisons (that is, only by checking whether Ali]