What is the average lap time for Sebastian Vettel in the 2009 Chinese Grand Prix?
AVG(time);
SELECT AVG(T2.milliseconds) FROM races AS T1 INNER JOIN lapTimes AS T2 ON T2.raceId = T1.raceId INNER JOIN drivers AS T3 ON T3.driverId = T2.driverId WHERE T3.forename = 'Sebastian' AND T3.surname = 'Vettel' AND T1.year = 2009 AND T1.name = 'Chinese GrAND Prix'