CREATE TABLE "double_premiership_teams" (
  "season" real,
  "premier" text,
  "runner_up" text,
  "score" text,
  "venue" text,
  "attendance" real,
  "premiership" text
);

Question: If the season is before 2000, the runner up was north melbourne, and it's the pre-season cup, what's the sum of attendees?
SQL: SELECT SUM("attendance") FROM "double_premiership_teams" WHERE "premiership"='pre-season cup' AND "runner_up"='north melbourne' AND "season"<2000;