Translate the following inference to logic notation: There is at least one x for which z_4 is a cashier if and only if z_4 will play tennis. For all x, z_4 will play tennis and z_4 is an artist. Therefore there is at least one x for which z_4 is a cashier.
exists x: P(x) <-> Q(x). forall x: Q(x) and R(x). Therefore exists x: P(x).