proposition: Lemma BRsum_Mlele0 a b c : a <=r c -> b <=r \0r -> (a +r b) <=r c.
proof: Proof. by move => pa pb; move: (BRsum_Mlele pa pb); rewrite (BRsum_0r (proj32 pa)). Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)