CREATE TABLE "table1_26198709_1" (
  "no" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "u_s_viewers_million" text,
  "rank_week" real,
  "original_air_date" text,
  "production_code" text
);

Question: What is the production code for the episode that had 18.07 million viewers? 
SQL: SELECT "production_code" FROM "table1_26198709_1" WHERE "u_s_viewers_million"='18.07';

Question: What is the weeks rank for the episode with the production code 1alf05? 
SQL: SELECT MAX("rank_week") FROM "table1_26198709_1" WHERE "production_code"='1ALF05';

Question: How many air dates does the episode with 15.50 million viewers have? 
SQL: SELECT COUNT("original_air_date") FROM "table1_26198709_1" WHERE "u_s_viewers_million"='15.50';

Question: Who wrote the episode with 18.07 million viewers? 
SQL: SELECT "written_by" FROM "table1_26198709_1" WHERE "u_s_viewers_million"='18.07';