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: exists x_15: U(x_15) <-> T_4(x_15). forall x_15: T_4(x_15) or ~Q_15(x_15). forall x_15: W_2(x_15). forall x_15: W_2(x_15) -> Q_15(x_15).
forall x_15: Q_15(x_15) can be inferred via the universal modus ponens rule. forall x_15: Q_15(x_15) -> T_4(x_15) can be inferred via the universal rewriting rule. exists x_15: U(x_15) -> T_4(x_15) can be inferred via the existential biconditional elimination rule. exists x_15: T_4(x_15) -> U(x_15) can be inferred via the existential biconditional elimination rule.