Hydrogen gas will not reduce

Sodium dissolved in liquid ammonia conducts electricity because ________.

Write down the balanced equations for the reaction when:
Calcium phosphate is heated with a mixture of sand and carbon;

$$P\left( {A \cup B} \right) = P\left( {A \cap B} \right)$$ if and only if the relation between $$P(A)$$ and $$P(B)$$ is .............