What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? forall x_1: P_2(x_1). exists x_1: U(x_1) <-> P_2(x_1).
exists x_1: U(x_1) -> P_2(x_1). exists x_1: P_2(x_1) -> U(x_1).