What was the place in season 8 with a rank by average at 139?
CREATE TABLE "average_scores_of_all_couples" (
  "rank_by_average" text,
  "place" text,
  "perfect_40s" text,
  "total" text,
  "number_of_dances" text,
  "season" text,
  "average" text
);
SELECT "place" FROM "average_scores_of_all_couples" WHERE "season"='8' AND "rank_by_average"='139';