What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? forall z: ~U(z). forall z: W(z) <-> S_2(z). exists z: U(z) <-> S_2(z).
forall z: W(z) -> S_2(z). exists z: U(z) -> S_2(z). forall z: S_2(z) -> W(z). exists z: S_2(z) -> U(z). exists z: ~S_2(z).