Translate the following inference to logic notation: For all x, z is a janitor if and only if z is a taxi driver. For all x, z is a musician or z is not a janitor. Therefore for all x, if z were a taxi driver, then z is a musician.
forall x: P(x) <-> Q(x). forall x: R(x) or ~P(x). Therefore forall x: Q(x) -> R(x).