Teoria dos Conjuntos - Exercício 4 - Nível Hard

(ITA 2012) Let A and B be two disjoint sets, both finite and non-empty, such that n(P(A)⋃P(B))+1 = n(P(A⋃B)). Then, the difference n(A)-n(B) can assume: a) A single value b) Only two distinct values c) Only three distinct values d) Only four distinct values e) More than four distinct values Solution