Translate the following inference to logic notation: For all x, if y plays squash, then y is running. For all x, if y goes running, then y is playing squash. For all x, if y goes running, then y is playing squash. Therefore for all x, y will go running if and only if y will play squash.
forall x: P(x) -> Q(x). forall x: Q(x) -> P(x). forall x: Q(x) -> P(x). Therefore forall x: Q(x) <-> P(x).