Translate the following inference to logic notation: For all x, if z_2 were an astronaut, then z_2 is a sailor. For all x, z_2 is not an astronaut. There is at least one x for which z_2 is a sailor if and only if z_2 is an astronaut. Therefore there is at least one x for which z_2 is not a sailor.
forall x: P(x) -> Q(x). forall x: ~P(x). exists x: Q(x) <-> P(x). Therefore exists x: ~Q(x).