user: Question: What is the release date for Ben 10: Alien Force Volume 9 on DVD?
Columns: ['DVD title', 'Season', 'Aspect ratio', 'Episode count', 'Time length', 'Release date']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Ben 10: Alien Force Volume 1', 'Season One', '4:3', 5.0, '110 Minutes', 'October 21, 2008']
SQL:

assistant: SELECT "Release date" FROM "Table" WHERE "DVD title" = 'Ben 10: Alien Force Volume 9';