Translate the following inference to logic notation: For all x, x_5 is not a server. For all x, if x_5 were a mechanic, then x_5 is a server. There is at least one x for which x_5 is sad if and only if x_5 is a cashier. For all x, if x_5 were a cashier, then x_5 is a mechanic. Therefore there is at least one x for which x_5 is not sad.
forall x: ~P(x). forall x: Q(x) -> P(x). exists x: R(x) <-> S(x). forall x: S(x) -> Q(x). Therefore exists x: ~R(x).