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12. If A = { 1, 2, 3, 4, 5, 6, 7), B = {2, 4, 6, 8, 10, 12), and f: A B where f = (1, 2), (2, 6), (3,6), (4, 8), (5,6), (6, 8), (7, 12)], determine the preimage of B under f in each of the following cases. a) Bi = {2} c) Bi = {6,8} e) Bi = {6, 8, 10, 12) d) Bi 6, 8, 10) f)Bi.{10, 12)