I'm a little rusty and need to get back into the swing of things after not seeing this stuff for a while so I need a little push. Hope someone can help!

Prove or Disprove:

for any three sets A,B,C,

(a) A∪(B−C)⊂(A∪B)−(A∪C) Is this disproven by the sets A={1,2}, B={3,4}, and C={1,2}?

(b) (A∪B)−(A∪C)⊂A∪(B−C)

For any four sets A,B,C,D prove or disprove:

(c) (A×B)∪(C×D)=(A∪C)×(B∪D)

(d)(A×B)∩(C×D)=(A∩C)×(B∩D)