intuition.
eapply leRat_trans.
eapply ratAdd_leRat_compat_l; eauto.
rewrite ratAdd_comm.
eapply leRat_trans.
apply ratAdd_leRat_compat_l; eauto.
rewrite ratAdd_comm.
intuition.
Qed.

Theorem ratMult_leRat_compat : forall (r1 r2 r3 r4 : Rat),
leRat r1 r2 ->
leRat r3 r4 ->
leRat (ratMult r1 r3) (ratMult r2 r4).