4. State whether each set of ordered pairs is a function. How about its inverse? a) {(2, 4), (3, 5), (7, 9), (2, -5), (3,-7)} b) 1 (5, 4), (4, 3), (3, 2), (2, 1), (1, 0) } c) { (-1, 6), (0, -6), (1, -6), (1, -6), (2, -6) }