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_9: R_7(x_9) -> P_9(x_9). forall x_9: P_7(x_9) or U_2(x_9). forall x_9: ~P_7(x_9) or R_7(x_9). exists x_9: U_2(x_9) -> P_9(x_9). forall x_9: P_9(x_9) -> U_2(x_9).
forall x_9: R_7(x_9) -> U_2(x_9) can be inferred via the universal transitivity rule. forall x_9: U_2(x_9) or R_7(x_9) can be inferred via the universal resolution rule. exists x_9: U_2(x_9) <-> P_9(x_9) can be inferred via the existential biconditional introduction rule. exists x_9: P_9(x_9) <-> U_2(x_9) can be inferred via the existential biconditional introduction rule.