Let A = {3, 6, 12, 15, 18, 21), B = {4, 8, 12, 16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16} and D = {5, 10, 15, 20}. Find: (i) A – B (ii) A – C (iii) A – D (iv) B – A (v) C – A (vi) D – A ((vii) B – C (viii) B – D