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: R_2(z) <-> U_1(z). forall z: U_1(z) -> W_2(z). forall z: W_2(z) -> R_2(z).
forall z: U_1(z) -> R_2(z) can be inferred via the universal transitivity rule. forall z: R_2(z) -> U_1(z) can be inferred via the universal biconditional elimination rule. forall z: U_1(z) -> R_2(z) can be inferred via the universal biconditional elimination rule.