1. The problem statement, all variables and given/known data Consider the following magma, S is not empty; P(S) is the power set. (P(S), U) Now, let A and B be in P(S). What is the GCD of A and B? 2. Relevant equations 3. The attempt at a solution If I choose a common divisor of A and B under unions, call it X, I get that X is a subset of A and B as the only requirement. The only way I can interpret "GCD" is that X is the largest such set. Then X = (A intersect B.) Agree?