What is the sum of the weight of the race with a 1st pos'n and a 8f distance?
CREATE TABLE "1929_30_season_as_a_three_year_old" (
  "result" text,
  "race" text,
  "distance" text,
  "weight" real,
  "winner_or_2nd" text,
  "pos_n" text
);
SELECT SUM("weight") FROM "1929_30_season_as_a_three_year_old" WHERE "pos_n"='1st' AND "distance"='8f';