What is the total share for an episode with an air date of November 19, 2007?
CREATE TABLE "u_s_ratings" (
  "episode" text,
  "air_date" text,
  "rating" real,
  "share" real,
  "18_49_rating_share" text,
  "viewers_m" real,
  "weekly_rank" real
);
SELECT SUM("share") FROM "u_s_ratings" WHERE "air_date"='november 19, 2007';