Prove that the running time of Shellsort, using the increment sequence suggested by Hibbard, is (N3/2) in the worst case. Hint: You can prove the bound by considering the special case of what Shellsort does when all elements are either 0 or 1. Set a[i] = 1 if i is expressible as a linear combination of ht, ht−1, . . . , ht/2+1 and 0 otherwise.