analysis of aglorithm

Assume randomized insertion sort computes a random permutation of the input array, and then runs deterministic insertion sort on this permutation. (a) What is the runtime of deterministic insertion sort on the input array [n, n-1, n-2, ..., 3, 2, 1]? (b) What is the best-case runtime of randomized insertion sort on the input array [n, n - 1, n - 2, ..., 3, 2, 1]? Describe what causes this best-case behavior