How many episodes with the production code CA106 are there?
CREATE TABLE "table1_25740548_2" (
  "series_num" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "production_code" text,
  "u_s_viewers_million" text
);
SELECT COUNT("written_by") FROM "table1_25740548_2" WHERE "production_code"='CA106';