Translate the following inference to logic notation: For all x, y is a lawyer if and only if y is a janitor. Mary is drinking water if and only if it is snowing. It is not snowing. Mary is drinking water if and only if John is a lawyer. Therefore John is not a janitor.
forall x: P(x) <-> Q(x). p <-> q. ~q. p <-> P(a). Therefore ~Q(a).