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: S(z) <-> U_2(z). exists z: U_2(z) or ~S(z).
exists z: S(z) -> U_2(z) can be inferred via the existential rewriting rule. forall z: S(z) -> U_2(z) can be inferred via the universal biconditional elimination rule. forall z: U_2(z) -> S(z) can be inferred via the universal biconditional elimination rule.