(a) Calculate A B C for A = {1, 2, 3, 5}, B = {1, 2, 4, 6}, C = {1, 3, 4, 7}.

Note that the symmetric difference operation is associative: (A B) C = A (B C).

(b) Let A, B, and C be any finite sets. Give a concise description for which elements from A, B, and C are in A B C.

(c) Let A₁, A₂, , A_n be any finite sets. Give a concise description for which elements from A₁, A₂, , A_n are in A₁ A₂ A_n

(d) Give an example showing that subtraction is not associative: A - (B - C) (A - B) - C.