What is the production code that had 24.8 million u.s. viewers?
CREATE TABLE "table1_27713890_1" (
  "no_in_series" real,
  "no_in_season" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "production_code" real,
  "u_s_viewers_millions" text
);
SELECT MAX("production_code") FROM "table1_27713890_1" WHERE "u_s_viewers_millions"='24.8';