1.
Let E1E_1 and E2E_2 be two events such that the conditional probabilities P(E1E2)=12P(E_1 \mid E_2) = \dfrac{1}{2}, P(E2E1)=12P(E_2 \mid E_1) = \dfrac{1}{2} and P(E1E2)=14P(E_1 \cap E_2) = \dfrac{1}{4}. Then: