What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? forall x_19: P_19(x_19) <-> Q_19(x_19). forall x_15: Q_19(x_15).
forall x_19: P_19(x_19) -> Q_19(x_19). forall x_19: Q_19(x_19) -> P_19(x_19).