Table:
text: 2008 Chinese motorcycle Grand Prix
250cc classification
250cc classification
Rider Manufacturer Laps Time_ Grid
Russel Gomez Aprilia 21 +2:13.718 23
Alex Baldolini Aprilia 14 Retirement 20
Julian Simon KTM 5 Retirement 4
Thomas Luthi Aprilia 5 Retirement 6
Karel Abraham Aprilia 4 Retirement 17
Lukas Pesek Aprilia 2 Retirement 14
Manuel Poggiali Gilera 0 Accident 8

text: 2008 Chinese motorcycle Grand Prix
250cc classification
250cc classification
Rider Manufacturer Laps Time_ Grid
Mika Kallio KTM 21 48:12.217 3
Hiroshi Aoyama KTM 21 +3.238 11
Mattia Pasini Aprilia 21 +13.811 7
Marco Simoncelli Gilera 21 +18.474 5
Alex Debon Aprilia 21 +21.066 12
Hector Barbera Aprilia 21 +25.158 2
Yuki Takahashi Honda 21 +29.900 10
Ratthapark Wilairot Honda 21 +39.871 18
Aleix Espargaro Aprilia 21 +48.344 15
Héctor Faubel Aprilia 21 +55.470 13
Roberto Locatelli Gilera 21 +55.832 9
Alvaro Bautista Aprilia 21 +1:00.442 1
Eugene Laverty Aprilia 21 +1:00.732 19
Fabrizio Lai Gilera 21 +1:36.975 16
Doni Tata Pradita Yamaha 21 +1:37.080 21
Imre Toth Aprilia 21 +1:45.018 22

Question: What is the time when the laps are less than 21, the manufacturer is Aprilia, the grid is less than 17 and the rider is Thomas Lüthi in the 250cc classification of the 2008 Chinese Motorcycle Grand Prix?