What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? forall x: ~U(x). forall x: U_1(x) -> U_3(x). forall x: U_3(x) -> U_1(x). exists x: U_3(x) <-> U(x).
forall x: U_1(x) <-> U_3(x). forall x: U_3(x) <-> U_1(x). exists x: U_3(x) -> U(x). exists x: U(x) -> U_3(x). exists x: ~U_3(x).