3. Proof by construction:
(a) Prove that there are integers such that a^2 | b^3 but a |/ b.
(b) Show that there are positive integers x, a, b, n such that a ≡ b mod n but x^a ≡/ x^b mod n.
(c) Show that there are two different graphs on 10 vertices all of whose vertices have degree
3 by constructing one such graph which is connected, and one which is not connected.