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_6: P_6(x_6) -> Q_6(x_6). forall x_6: P_6(x_6). exists x_6: U(x_6) -> ~S_1(x_6). forall x_6: S_1(x_6).
forall x_6: Q_6(x_6) can be inferred via the universal modus ponens rule. exists x_6: ~U(x_6) can be inferred via the existential modus tollens rule. forall x_6: P_6(x_6) and S_1(x_6) can be inferred via the universal conjunction rule. forall x_6: S_1(x_6) and P_6(x_6) can be inferred via the universal conjunction rule.