Translate the following inference to logic notation: There is at least one x for which if x_6 were sad, then x_6 is a server. For all x, x_6 is a cashier if and only if x_6 is a server. For all x, x_6 is not a cashier. For all x, if x_6 were a server, then x_6 is sad. Therefore there is at least one x for which x_6 is not sad.
exists x: P(x) -> Q(x). forall x: R(x) <-> Q(x). forall x: ~R(x). forall x: Q(x) -> P(x). Therefore exists x: ~P(x).