Translate the following inference to logic notation: There is at least one x for which if x_6 were sad, then x_6 is working. For all x, x_6 is sad. For all x, if x_6 sleeps, then x_6 is playing tennis. For all x, if x_6 works, then x_6 is sleeping. Therefore there is at least one x for which x_6 will play tennis.
exists x: P(x) -> Q(x). forall x: P(x). forall x: R(x) -> S(x). forall x: Q(x) -> R(x). Therefore exists x: S(x).