user: ### NOW ANSWER:
Question: What kind of Winning driver has a Winning constructor of Mercer?
Columns: ['Name', 'Circuit', 'Date', 'Winning driver', 'Winning constructor', 'Report']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Vanderbilt Cup', 'Santa Monica', '26 February', 'Ralph DePalma', 'Mercedes', 'Report']
SQL:

assistant: SELECT "Winning driver" FROM "Table" WHERE "Winning constructor" = 'Mercer';