CREATE TABLE "table1_23177573_1" (
  "no" real,
  "num" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "u_s_viewers_million" text,
  "rank_week" real,
  "original_air_date" text
);

Question: What is the original air date of the episode that had a week ranking of 21?
SQL: SELECT "original_air_date" FROM "table1_23177573_1" WHERE "rank_week"=21;

Question: What was the week ranking of the episode written by Russel Friend & Garrett Lerner? 
SQL: SELECT "rank_week" FROM "table1_23177573_1" WHERE "written_by"='Russel Friend & Garrett Lerner';

Question: What was the week ranking of the episode written by Thomas L. Moran and directed by Andrew Bernstein?
SQL: SELECT "rank_week" FROM "table1_23177573_1" WHERE "written_by"='Thomas L. Moran' AND "directed_by"='Andrew Bernstein';