Problem
1. Show that (X - A) (X - B) = X - (A ∩ B), for any three sets X, A, and B.
2. Consider again the modification of the deterministic version of the quicksort algorithm so that, instead of selecting the last element in an n-element sequence as the pivot, we choose the element at index ...ln/2.... Describe the kind of sequence that would cause this version of quick-sort to run in (n 2 ) time.