proposition: Lemma set_incl_setI_r {A} (s1 s2 s3 : set A) : s2 \subset s3 -> (s1 :&: s2) \subset s3.
proof: Proof. firstorder. Qed.
imports: mathcomp.ssreflect.ssreflect Classes.RelationClasses Classes.Morphisms List Tactics mathcomp(ssrfun ssrbool ssrnat seq)