What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? forall x_1: ~U_2(x_1). exists x_1: R_4(x_1) -> U_2(x_1). forall x_1: R(x_1) <-> R_4(x_1).
exists x_1: ~R_4(x_1). forall x_1: R(x_1) -> R_4(x_1). forall x_1: R_4(x_1) -> R(x_1).