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: U_3(z) -> W(z). forall z: W(z) -> U_3(z). forall z: ~U_3(z). exists z: S(z) <-> W(z).
forall z: ~W(z) can be inferred via the universal modus tollens rule. forall z: U_3(z) <-> W(z) can be inferred via the universal biconditional introduction rule. forall z: W(z) <-> U_3(z) can be inferred via the universal biconditional introduction rule. exists z: S(z) -> W(z) can be inferred via the existential biconditional elimination rule. exists z: W(z) -> S(z) can be inferred via the existential biconditional elimination rule.