Solve this. Shouldn't it be 6 hours ?

46.    ​The radius of the orbit of a geosynchronous satellite is 36000 km, then the period of revolution of a satelite with its orbital radius 9000 km would be 

(1)      ​24 hrs                    ​  ​(2)      ​12 hrs

(3)      ​6 hrs                      ​  ​(4)      ​3 hrs