(a) n(A U B) = n(A) + n(B) - n(A ∩ B) = 100 + 80 - 40 = 140. (b) n(A^c) = n(U) - n(A) = 200 - 100 = 100. (c) The set A ∩ B^c consists of those elements from A that do not belong to B. In other words, A ∩ Bc = A \ (A ∩ B). THEREFORE, n(A ∩ B^c) = n(A) - n(A ∩ B) = 100 - 40 = 60.