Translate the following inference to logic notation: There is at least one x for which if x_4 were a taxi driver, then x_4 is a musician. For all x, x_4 will play tennis if and only if x_4 is a musician. For all x, x_4 will not play tennis. For all x, if x_4 were a musician, then x_4 is a taxi driver. Therefore there is at least one x for which x_4 is not a taxi driver.
exists x: P(x) -> Q(x). forall x: R(x) <-> Q(x). forall x: ~R(x). forall x: Q(x) -> P(x). Therefore exists x: ~P(x).