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 y_4: U_2(y_4) -> P_2(y_4). exists y_4: P_2(y_4) -> Q_4(y_4). forall y_4: ~Q_4(y_4). forall y_4: Q_4(y_4) -> U_2(y_4).
exists y_4: ~P_2(y_4) can be inferred via the existential modus tollens rule. forall y_4: Q_4(y_4) -> P_2(y_4) can be inferred via the universal transitivity rule. exists y_4: P_2(y_4) -> U_2(y_4) can be inferred via the existential transitivity rule. exists y_4: U_2(y_4) -> Q_4(y_4) can be inferred via the existential transitivity rule.