What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? exists z: U(z) <-> R_1(z). forall z: S_2(z) <-> U(z). forall z: ~R_1(z).
forall z: S_2(z) -> U(z). exists z: U(z) -> R_1(z). forall z: U(z) -> S_2(z). exists z: R_1(z) -> U(z). exists z: ~U(z).