Discrete Mathematics Please show all work Let A = {q, r, s, t} and B = { 17, 18, 19, 20} . Determine which of the following are functions. Explain why or why not. l. a, f A B, where f-{(q, 17), (r, 18), (s, 19), (t, 20)) b, g A B, where g = {(q, 17), (q, 20), (s, 19), (t, 20), (r, 20)) c, h A B, where h = {(q, 17), (r, 20), (s, 19), (t, 20)) d. k BB,where k={(17, 17), (18,17), (19,17), (20,18)) e. I .X A, where I = {(q, r), (q, s), (s, r), (t, t))