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_15: P(x_15) -> Q(x_15). forall x_15: ~R(x_15). forall x_15: Q(x_15) -> Q_7(x_15). exists x_15: P(x_15) <-> Q(x_15). forall x_15: Q_7(x_15) -> R(x_15).
forall x_15: ~Q_7(x_15) can be inferred via the universal modus tollens rule. forall x_15: P(x_15) -> Q_7(x_15) can be inferred via the universal transitivity rule. forall x_15: Q(x_15) -> R(x_15) can be inferred via the universal transitivity rule. exists x_15: P(x_15) -> Q(x_15) can be inferred via the existential biconditional elimination rule. exists x_15: Q(x_15) -> P(x_15) can be inferred via the existential biconditional elimination rule.