proposition: Lemma markov (r : R) : 0 < r -> `Pr[ X >= r ] <= `E X / r.
proof: Proof. by move=> r0; rewrite leR_pdivl_mulr // mulRC; exact/Ex_lb. Qed.
imports: mathcomp(all_ssreflect ssralg ssrnum matrix) mathcomp(Rstruct reals) Reals Lra ssrR Reals_ext realType_ext logb ssr_ext ssralg_ext bigop_ext fdist