How many production codes are there for the episode that had 4.36 million u.s. viewers?
CREATE TABLE "table1_28037619_2" (
  "no" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "production_code" real,
  "u_s_viewers_million" text
);
SELECT COUNT("production_code") FROM "table1_28037619_2" WHERE "u_s_viewers_million"='4.36';