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(z) <-> U_2(z). forall z: P(z) -> Q_4(z). s -> Q_4(d_4). forall z: Q_4(z) -> P(z). forall z: ~U_2(z).
forall z: P(z) <-> Q_4(z) can be inferred via the universal biconditional introduction rule. forall z: Q_4(z) <-> P(z) can be inferred via the universal biconditional introduction rule. forall z: P(z) -> U_2(z) can be inferred via the universal biconditional elimination rule. forall z: U_2(z) -> P(z) can be inferred via the universal biconditional elimination rule. forall z: ~P(z) can be inferred via the universal biconditional elimination rule.