Table:
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

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

Question: What is the time when the laps are less than 21 and the grid is more than 17 for the 2008 Chinese Motorcycle Grand Prix 250cc classification?