Translate the following inference to logic notation: For all x, x_13 is a cashier if and only if x_13 is a sailor. There is at least one x for which x_13 is a sailor or x_13 is not a cashier. For all x, x_13 will play a game. For all x, if x_13 were a cashier, then x_13 is not playing a game. Therefore there is at least one x for which x_13 is not a sailor.
forall x: P(x) <-> Q(x). exists x: Q(x) or ~P(x). forall x: R(x). forall x: P(x) -> ~R(x). Therefore exists x: ~Q(x).