What is the rank number that aired october 26, 2007?
CREATE TABLE "weekly_ratings" (
  "num" real,
  "episode" text,
  "air_date" text,
  "timeslot_est" text,
  "season" text,
  "rating" text,
  "share" real,
  "18_49" text,
  "viewers_m" text,
  "rank_num" text
);
SELECT "rank_num" FROM "weekly_ratings" WHERE "air_date"='October 26, 2007';