user: Question: On September 10 during Strikeforce: Heavyweight Grand Prix Semifinals, what was the PPV buyrate?
Columns: ['Date', 'Event', 'Location', 'Attendance', 'PPV Buyrate']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['January 1', 'UFC 125: Resolution', 'Las Vegas , Nevada, USA', '12,874', '270,000']
SQL:

assistant: SELECT "PPV Buyrate" FROM "Table" WHERE "Date" = 'September 10' AND "Event" = 'Strikeforce: Heavyweight Grand Prix Semifinals';