What was Lewis Hamilton's final rank in the 2008 Australian Grand Prix?
final rank refers to positionOrder
SELECT T2.positionOrder FROM races AS T1 INNER JOIN results AS T2 ON T2.raceId = T1.raceId INNER JOIN drivers AS T3 ON T3.driverId = T2.driverId WHERE T3.forename = 'Lewis' AND T3.surname = 'Hamilton' AND T1.name = 'Australian Grand Prix' AND T1.year = 2008