33. Use a Karnaugh map to find the minimum AND-OR expression for x(a, b, c, d): "(a) (2, 3, 4, 5, 10, 12, 13) (b) (1, 5, 6, 7, 9, 12, 13, 15) (c) 2(0, 1, 2, 4, 6, 8, 10) (e) (2, 4, 5, 11, 13, 15) (f) (1, 2, 4, 5, 6, 7, 12, 15)