Translate the following inference to logic notation: For all x, x_5 is sad if and only if x_5 is a janitor. For all x, if x_5 climbs a mountain, then x_5 is drinking water. For all x, x_5 is a janitor if and only if x_5 will climb a mountain. For all x, x_5 will not drink water. Therefore for all x, x_5 is not sad.
forall x: P(x) <-> Q(x). forall x: R(x) -> S(x). forall x: Q(x) <-> R(x). forall x: ~S(x). Therefore forall x: ~P(x).