1. a) Suppose an algorithm solves problems by dividing them into five subproblems of half the size, recursively solving each subproblem, and then combining the solutions in O(n) time. What is the Big-O class of its runtime?Explain. b) Suppose an algorithm solves problems by dividing them into four subproblems of one third the size, recursively solving each subproblem, and then combining the solutions in O(n) time. What is the Big-O class of its runtime?Explain.