What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? forall y: P_3(y) -> Q_3(y). forall y: Q_3(y) -> P_3(y). forall y: Q_3(y) <-> P_3(y).
forall y: P_3(y) <-> Q_3(y). forall y: Q_3(y) <-> P_3(y). forall y: Q_3(y) -> P_3(y). forall y: P_3(y) -> Q_3(y).