CREATE TABLE "table1_21304155_1" (
  "no_in_series" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "production_code" text,
  "u_s_viewers_millions" text
);

Question: What is the production code of the episode directed by David Solomon? 
SQL: SELECT "production_code" FROM "table1_21304155_1" WHERE "directed_by"='David Solomon';

Question: Who wrote the episode with the production code of BN103? 
SQL: SELECT "written_by" FROM "table1_21304155_1" WHERE "production_code"='BN103';

Question: What was the original air date of the episode that had 4.08 million U.S. viewers? 
SQL: SELECT "original_air_date" FROM "table1_21304155_1" WHERE "u_s_viewers_millions"='4.08';