user: ### NOW ANSWER:
Question: what is the time when laps is less than 21, manufacturer is Aprilia, grid is less than 17 and the rider is Thomas Luthi?
Columns: ['Rider', 'Manufacturer', 'Laps', 'Time', 'Grid']
Types: ['text', 'text', 'real', 'text', 'real']
Sample row: ['Mika Kallio', 'KTM', 21.0, '48:12.217', 3.0]
SQL:

assistant: SELECT "Time" FROM "Table" WHERE "Laps" < 21.0 AND "Manufacturer" = 'Aprilia' AND "Grid" < 17.0 AND "Rider" = 'Thomas Luthi';