Let A = {x Zx = 3k for some k Z} and let B = {x Zx = 6k + 3for some k Z}. (a) Prove that BCA by filling in the blanks: Let x E B. Since x E B, Therefore, as required. (b) Is ACB? Explain giving reasons. (c) Is A = B? Explain giving reasons. Factoring out by 3 gives x = 2 mark(s) 1 mark(s) 1 mark(s) 4 marks total