(a) Let f: A→B, where |A| = 25, B = {x, y, z}, and | f-l(x) | = 10, | f-l(y) | = 10, |f-1(z)| = 5. If we define the relation R on A by a R b if a, b ∈ A and f(a) = f(b), how many ordered pairs are there in the relation R?
(b) For n, n1, n2, n3, n4 ∈ Z+, let f: A→B, where |A| = n, B = {w, x, y, z}, |f-1(w)| = n1, | f-1(x) | = n2, | f-1(y) | = n3, | f-1(z) | = n4, and n1 + n2 + n3 + n4 = n. If we define the relation R on A by a R b if a, b ∈ A and f (a) = f(b), how many ordered pairs are there in the relation R?