Translate the following inference to logic notation: For all x, x_12 is a sailor if and only if x_12 will work. For all x, x_12 will drink water if and only if x_12 is a sailor. There is at least one x for which if x_12 works, then x_12 is drinking water. Therefore there is at least one x for which x_12 is a sailor if and only if x_12 will drink water.
forall x: P(x) <-> Q(x). forall x: R(x) <-> P(x). exists x: Q(x) -> R(x). Therefore exists x: P(x) <-> R(x).