Translate the following inference to logic notation: For all x, if x_6 were a soldier, then x_6 is a cashier. There is at least one x for which if x_6 were a cashier, then x_6 is a server. For all x, if x_6 plays squash, then x_6 is a soldier. For all x, if x_6 were a server, then x_6 is playing squash. Therefore there is at least one x for which x_6 will play squash if and only if x_6 is a cashier.
forall x: P(x) -> Q(x). exists x: Q(x) -> R(x). forall x: S(x) -> P(x). forall x: R(x) -> S(x). Therefore exists x: S(x) <-> Q(x).