CREATE TABLE table_20911 ("No. in series" TEXT, "No. in season" TEXT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original airdate" TEXT, "Production code" TEXT)

What is the production code for episode 15 in season 3?
SELECT "Production code" FROM table_20911 WHERE "No. in season" = '15'
SELECT "Production code" FROM "table_20911" WHERE "No. in season" = '15'