user: Question: Who wrote the episode that had 12.15 million viewers?
Columns: ['Series #', 'Season #', 'Title', 'Directed by', 'Written by', 'Original air date', 'U.S. viewers (millions)']
Types: ['real', 'real', 'text', 'text', 'text', 'text', 'text']
Sample row: [137.0, 1.0, '"Closure"', 'John Polson', 'Jan Nash, Bruce Ramussen', 'September23,2008', '11.28']
SQL:

assistant: SELECT "Written by" FROM "Table" WHERE "U.S. viewers (millions)" = '12.15';