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: R_3(x) -> Q(x). forall x: ~Q(x). forall x: S(x) -> R_3(x). exists x: R_3(x) -> S(x).
forall x: ~R_3(x) can be inferred via the universal modus tollens rule. forall x: S(x) -> Q(x) can be inferred via the universal transitivity rule. exists x: R_3(x) <-> S(x) can be inferred via the existential biconditional introduction rule. exists x: S(x) <-> R_3(x) can be inferred via the existential biconditional introduction rule.