proposition: Lemma Exercise1_21p r: total_order r -> order (quotient_order r (scattered_equiv r)).
proof: Proof. move => tor. move: (Exercise1_21i tor) (Exercise1_21j tor)(Exercise1_21o tor) => p1 p2 p3. by move: tor => [or _]; apply: Exercise1_2d. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)