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_1: P(z_1) <-> Q_3(z_1). ~w. w -> Q_3(a_9). Q_3(a_9) -> w.
~Q_3(a_9) can be inferred via the modus tollens rule. forall z_1: P(z_1) -> Q_3(z_1) can be inferred via the universal biconditional elimination rule. forall z_1: Q_3(z_1) -> P(z_1) can be inferred via the universal biconditional elimination rule.