Given an integral domain (D, +, •) with zero element z, let a, b ∈ D with ab ≠ z. (a) If a3 = b3 and a5 = b5, prove that a = b. (b) Let m, n ∈ Z+ with gcd(m, n) = 1. If am = bm and an = bn, prove that a = b.