Let A and B be sets. Prove that A ~ B implies that P(A) ~ P(B), where P(A): power set of A and P(B): power set of B.

I'm not sure how to approach this problem. My thoughts are to try to construct a bijective function g: P(A) -> P(B) and then use the fact A~B to help show this is a bijection. But I am not sure how to define g.