What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? exists x: R(x) <-> U_4(x). forall x: U_3(x) <-> R(x).
forall x: U_3(x) -> R(x). exists x: R(x) -> U_4(x). forall x: R(x) -> U_3(x). exists x: U_4(x) -> R(x).