Translate the following inference to logic notation: There is at least one x for which if x_4 drinks water, then x_4 is working. For all x, x_4 will drink water if and only if x_4 will play tennis. Therefore there is at least one x for which if x_4 plays tennis, then x_4 is working.
exists x: P(x) -> Q(x). forall x: P(x) <-> R(x). Therefore exists x: R(x) -> Q(x).