Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
what is the time when laps is less than 21, manufacturer is aprilia, grid is less than 17 and the rider is thomas luthi?

### Inputs:
table_name: table, columns: ['Rider', 'Manufacturer', 'Laps', 'Time', 'Grid']

### Response:
SELECT Time FROM table WHERE Laps < 21 AND Manufacturer = aprilia AND Grid < 17 AND Rider = thomas luthi