who is the manufacturer is no.50?
CREATE TABLE "by_season" (
  "season" real,
  "driver" text,
  "owner" text,
  "no" real,
  "manufacturer" text,
  "starts" text,
  "wins" real,
  "top_tens" real,
  "poles" real,
  "points_margin" text
);
SELECT "manufacturer" FROM "by_season" WHERE "no"=50;