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_4: Q_4(x_4) -> U(x_4). exists x_4: ~Q_4(x_4). forall x_4: U(x_4) <-> Q_4(x_4).
forall x_4: U(x_4) -> Q_4(x_4) can be inferred via the universal biconditional elimination rule. forall x_4: Q_4(x_4) -> U(x_4) can be inferred via the universal biconditional elimination rule. exists x_4: ~U(x_4) can be inferred via the existential biconditional elimination rule.