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 x_1: ~Q_3(x_1). forall x_1: S(x_1) -> Q_3(x_1). forall x_1: S(x_1) <-> P_4(x_1).
forall x_1: ~S(x_1) can be inferred via the universal modus tollens rule. forall x_1: S(x_1) -> P_4(x_1) can be inferred via the universal biconditional elimination rule. forall x_1: P_4(x_1) -> S(x_1) can be inferred via the universal biconditional elimination rule.