Translate the following inference to logic notation: For all x, if z were an office clerk, then z is a janitor. There is at least one x for which if z were a janitor, then z is an office clerk. For all x, if z drinks water, then z is an office clerk. For all x, if z were an office clerk, then z is drinking water. Therefore there is at least one x for which if z drinks water, then z is a janitor.
forall x: P(x) -> Q(x). exists x: Q(x) -> P(x). forall x: R(x) -> P(x). forall x: P(x) -> R(x). Therefore exists x: R(x) -> Q(x).