how many episode have 8.4 millions  viewer.
CREATE TABLE "table1_2112766_1" (
  "episode" text,
  "broadcast_date" text,
  "run_time" text,
  "viewers_in_millions" text,
  "archive" text
);
SELECT COUNT("episode") FROM "table1_2112766_1" WHERE "viewers_in_millions"='8.4';