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_3: P_2(x_3) <-> U(x_3). forall x_3: P_2(x_3) or ~U(x_3).
forall x_3: U(x_3) -> P_2(x_3) can be inferred via the universal rewriting rule. exists x_3: P_2(x_3) -> U(x_3) can be inferred via the existential biconditional elimination rule. exists x_3: U(x_3) -> P_2(x_3) can be inferred via the existential biconditional elimination rule.