CREATE TABLE table_73321 ("No." FLOAT, "#" FLOAT, "Title" CLOB, "Directed by" CLOB, "Written by" CLOB, "U.S. viewers  ( million ) " CLOB, "Original air date" CLOB, "Production code" FLOAT)

What is the production code for the episode that had 9.18 million viewers (U.S.)?
SELECT MAX("Production code") FROM table_73321 WHERE "U.S. viewers (million)" = '9.18'
SELECT MAX("Production code") FROM "table_73321" WHERE "U.S. viewers (million)" = '9.18'