user: Question: What is the production code for the episode written by Kat Likkel & Denise Downer?
Columns: ['No. in series', 'No. in season', 'Title', 'Directed by', 'Written by', 'Original air date', 'Production code']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['40a', '1a', '"Battle of the Century"', 'Norton Virgien', 'Mark Steen & Peter Hixson', 'September13,1997', '401a']
SQL:

assistant: SELECT "Production code" FROM "Table" WHERE "Written by" = 'Kat Likkel & Denise Downer';