Translate the following inference to logic notation: For all x, if z_4 were an artist, then z_4 is happy. For all x, z_4 is not an electrician. For all x, if z_4 were happy, then z_4 is an artist. There is at least one x for which z_4 is an artist if and only if z_4 is an electrician. Therefore there is at least one x for which z_4 is not happy.
forall x: P(x) -> Q(x). forall x: ~R(x). forall x: Q(x) -> P(x). exists x: P(x) <-> R(x). Therefore exists x: ~Q(x).