Set Theoryhard
0:00.0

Let S={1,2,,8}S = \{1, 2, \dots, 8\}. For any subset XSX \subseteq S, let f(X)=xXxf(X) = \sum_{x \in X} x denote the sum of its elements (with f()=0f(\emptyset) = 0). Let us define two collections of subsets: $$\mathcal{A} = \left{ A \in P(S) : f(A) \text{ is even} \right}$

\mathcal{B} = \left\{ B \in P(S) : |B \cap \{1, 2, 3, 4\}| \ge 3 \right\}$$ Determine the cardinality of the intersection \mathcal{A} \cap \mathcal{B}$.