What is the average crowd of the 13.9 (87) Home Team Score?
CREATE TABLE "round_of_16" (
  "home_team" text,
  "home_team_score" text,
  "away_team" text,
  "away_team_score" text,
  "ground" text,
  "crowd" real,
  "date" text,
  "time" text
);
SELECT AVG("crowd") FROM "round_of_16" WHERE "home_team_score"='13.9 (87)';