How many drivers managed to finish the race in the 2008 Australian Grand Prix?
managed to finish the race refers to time is not null
SELECT COUNT(T2.driverId) FROM races AS T1 INNER JOIN results AS T2 ON T2.raceId = T1.raceId WHERE T1.name = 'Australian Grand Prix' AND T1.year = 2008 AND T2.time IS NOT NULL