What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? forall x_6: U(x_6) -> ~R_2(x_6). forall x_6: U(x_6) <-> S_4(x_6). forall x_6: S_4(x_6) <-> S(x_6). forall x_6: R_2(x_6).
forall x_6: ~U(x_6). forall x_6: U(x_6) -> S_4(x_6). forall x_6: S_4(x_6) -> S(x_6). forall x_6: S_4(x_6) -> U(x_6). forall x_6: S(x_6) -> S_4(x_6).