Let A = {a, b, c}. Then P(A) consists of the following subsets of A : Aa = 0, Ab = A, Ac = {a, b}, Aa = {a, c}, Ae = {b, c}, Af = {a}, A, = {b}, An = {c}. In one part of the proof of Theorem 11.17, it was established (using a contradiction argument) that A