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: exists z: T_2(z) -> S_4(z). forall z: U(z) <-> T_2(z). forall z: S_4(z) -> U(z).
exists z: T_2(z) -> U(z) can be inferred via the existential transitivity rule. forall z: U(z) -> T_2(z) can be inferred via the universal biconditional elimination rule. forall z: T_2(z) -> U(z) can be inferred via the universal biconditional elimination rule.