4.Let A, B and C be sets. Determine whether or not the following are valid. Justify your answer by using either set identities or membership tables. You can also use a counterexample to show that two sets are not equivalent. Notice that the difference between two sets A and B can be denotedA\B or AB. (a) A(BC)=(AC)B (b) (AB)(BA)=(AB) (c) (AB)(BA)=(AB) (d) (AC)(BC)=ABC (e) (BC)(AC)=AC=A(AC) (f) A(BC)=A(BC)