What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? forall z: R_4(z) <-> U_1(z). forall z: U_1(z) <-> R_4(z).
forall z: R_4(z) -> U_1(z). forall z: U_1(z) -> R_4(z). forall z: U_1(z) -> R_4(z). forall z: R_4(z) -> U_1(z).