What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? forall y_3: ~U(y_3). exists y_3: U_2(y_3) <-> U(y_3).
exists y_3: U_2(y_3) -> U(y_3). exists y_3: U(y_3) -> U_2(y_3). exists y_3: ~U_2(y_3).