\[\boxed{\mathbf{78.}}\]
\[P(A \cap B) \leq P(A);\ \]
\[P(A \cap B) \leq P(B).\]
\[P(A \cap B) = P(A) \cdot P(B);\]
\[0 \leq P(A) \leq 1;\]
\[0 \leq P(B) \leq 1.\]
\[Что\ и\ требовалось\ доказать.\]