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_2(x) -> Q_2(x). forall x: R_2(x) or S_3(x). forall x: Q_2(x) -> S_3(x). exists x: S_3(x) -> Q_2(x).
forall x: R_2(x) -> S_3(x) can be inferred via the universal transitivity rule. exists x: Q_2(x) can be inferred via the existential disjunction elimination rule. exists x: S_3(x) <-> Q_2(x) can be inferred via the existential biconditional introduction rule. exists x: Q_2(x) <-> S_3(x) can be inferred via the existential biconditional introduction rule.