user: Question: In how many different audition cities were the Bridgestone Arena auditions held?
Columns: ['Episode air date', 'Audition city', 'First audition date', 'Audition venue', 'Callback audition date', 'Callback venue', 'Golden tickets']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['January 19, 2011', 'East Rutherford, New Jersey', 'August 3, 2010', 'Izod Center', 'September 28–30, 2010', 'Liberty House Restaurant', '51']
SQL:

assistant: SELECT COUNT("Audition city") FROM "Table" WHERE "Audition venue" = 'Bridgestone Arena';