proposition: Lemma mxrankMfree m n p (A : 'M_(m, n)) (B : 'M_(n, p)) : row_free B -> \rank (A *m B) = \rank A.
proof: Proof. by move=> Bfree; rewrite -mxrank_tr trmx_mul eqmxMfull /row_full mxrank_tr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype finfun bigop finset fingroup perm order) mathcomp(div prime binomial ssralg finalg zmodp matrix)