3. Prove that the sets A = {2.n+1:n € N} and B = {3⋅n+2:n € N} of the odd numbers and the "multiples of 3 plus 2," respectively, have the same size by giving an explicit bijection f: A → B. (Hint: Try to construct first two bijections, g: A → N and another h: N → B, and construct f: A → B as their composition.)

b. Use the Sum Rule for two sets to show that |A UBUC| = |A| + |B| + |C| – |A U B| – |A U C| – |B U C| + |A n B n C| (Hint: start with A UBUC = A U (B U C)]

# 2. Prove that for all sets A and B, (A - B) N B = Ø. Proof (A Proof By Contradiction):