8. Let G = {[1], [5], [7], [11]}, where [a] = {x ∈ ℤ : x ≡ a (mod 12)}.
(a) Draw the Cayley table for (G, ·) where · is the operation of multiplication modulo 12.
(b) Use your Cayley table to prove that (G, ·) is a group. You may assume that the operation · is associative.
(c) From class we know that (ℤ₄, +) and (ℤ₂ × ℤ₂, +) are two non-isomorphic groups that each have four elements. Which one of these groups is isomorphic to (G, ·)? Explain your answer briefly.