CREATE TABLE "round_11" (
  "home_team" text,
  "home_team_score" text,
  "away_team" text,
  "away_team_score" text,
  "venue" text,
  "crowd" real,
  "date" text
);

Question: How big was the crowd in game that featured the visiting team of north melbourne?
SQL: SELECT "crowd" FROM "round_11" WHERE "away_team"='north melbourne';