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