Let and be two pairwise disjoint families of sets. Let and(a) Prove that is a family of pairwise disjoint sets.(b) Give an example to show that need not be pairwise disjoint.(c) Prove that if and are disjoint, then is pairwise disjoint.

L14 - 6 40 35 30 25 20 15 10 5 −4 −3 −2 −1 1 2 3 4 −5 f(x)=4 x +9 x − 12x +3