How many people attended the game where the home team scored 10.13 (73)?
CREATE TABLE "round_15" (
  "home_team" text,
  "home_team_score" text,
  "away_team" text,
  "away_team_score" text,
  "venue" text,
  "crowd" real,
  "date" text
);
SELECT AVG("crowd") FROM "round_15" WHERE "home_team_score"='10.13 (73)';