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: ~w_4. u_3 -> w_4. ~S(a_3). forall x: Q_4(x) <-> S(x).
~u_3 can be inferred via the modus tollens rule. ~w_4 and ~S(a_3) can be inferred via the conjunction rule. ~S(a_3) and ~w_4 can be inferred via the conjunction rule. forall x: Q_4(x) -> S(x) can be inferred via the universal biconditional elimination rule. forall x: S(x) -> Q_4(x) can be inferred via the universal biconditional elimination rule.