proposition: Lemma RmpsS_div a b: inc a BRms -> inc b BRps -> inc (a /r b) BRms.
proof: Proof. move => ap bp; rewrite /BRdiv BRprodC. apply:RpmsS_prod => //;exact: (RpsS_inv bp). Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)