What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: forall z: P_4(z) or ~U(z). exists z: P_4(z) -> U(z). forall z: U(z) -> P_4(z).
forall z: U(z) -> P_4(z) can be inferred via the universal rewriting rule. exists z: P_4(z) <-> U(z) can be inferred via the existential biconditional introduction rule. exists z: U(z) <-> P_4(z) can be inferred via the existential biconditional introduction rule.