I only need help with 5.18

Give an algorithm that takes O(n) comparisons . Can we solve the problem using asymptotically lesser number ofcom- parisons, i.e., in o(n) comparisons? Exercise 5.18. We are given a sequence of n positive numbers a1,... ,an and a fixed numberk > 0. We want to find a pair of numbers ai and aj such thatj i and aj-ai = k. If there is no such pair we want to output "false". This can be solved easily in (n2) time by examining all pairs of numbers. Your task is to give a divide and conquer algorithm that runs in O(n log n) time. Show the correctness ofyour algorithm and the analysis of its running time. Exercise 5.19. We are given an array A containing n numbers, and an integer k that divides n. We want to find k numbers x1,.r2, ...,k of A such