proposition: Lemma mult_commutes : commutes (cr_mult (c:=R)).
proof: Proof. elim CRing_is_CRing; auto. Qed.
imports: CoRN.tactics.CornTac CoRN.algebra.CSums CoRN.algebra.CAbMonoids Coq.Sorting.Permutation CoRN.util.SetoidPermutation Coq.Setoids.Setoid Coq.Classes.Morphisms Coq(Lia)