Hint Extern 0 (RIntro _ (respectful _ _) _ _) =>
eapply respectful_rintro : typeclass_instances.

Lemma respectful_relim {A B} (RA: relation A) (RB: relation B) f g m n P Q:
RElim RB (f m) (g n) P Q ->
RElim (respectful RA RB) f g (RA m n /\ P) Q.