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: P_9(x_9) -> U_4(x_9). forall x_9: P_9(x_9) or Q_9(x_9). forall x_9: Q_9(x_9) -> U_4(x_9). forall x_9: Q_1(x_9) -> S(x_9). exists x_9: U_4(x_9) -> Q_1(x_9).
exists x_9: U_4(x_9) -> S(x_9) can be inferred via the existential transitivity rule. exists x_9: P_9(x_9) -> Q_1(x_9) can be inferred via the existential transitivity rule. exists x_9: Q_9(x_9) -> Q_1(x_9) can be inferred via the existential transitivity rule. forall x_9: U_4(x_9) can be inferred via the universal disjunction elimination rule.