user: Question: What was the final number for the winning manufacturer with mercedes-benz, and a circuit of hockenheimring?
Columns: ['Round', 'Circuit', 'Date', 'Fastest lap', 'Winning driver', 'Winning team', 'Winning manufacturer']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, 'Hockenheimring', '28 May', 'Bernd Schneider', 'Bernd Schneider', 'HWA 1', 'Mercedes-Benz']
SQL:

assistant: SELECT "Round" FROM "Table" WHERE "Winning manufacturer" = 'mercedes-benz' AND "Circuit" = 'hockenheimring';