一題折舊問題 - 會計

On 1 Octber 2005 Dearing acquire a machine under the follow terms:
Hours $
------- -------
Manufacture's base price 1050000
Purchase discount(applying to base price only) 20%
Early settlement discount taken(on the payable
amount of the base cost only) 5%
Freight charges 30000
Electrical installation cost 28000
Staff training in use of machine 40000
Pre-production testing 22000
Purchase of three-year maintenance contract 60000
Estimated residual value 20000
Estimated life in machines hours 6000
Hours used-year ended 30 September 2006 1200
-year ended 30 September 2007 1800
-year ended 30 September 2008 850
On 1 October 2007, Dearing decided to upgrade the machine by adding new
components at a cost of 200000. This upgrade let to a reducton in the
production time per unit of the goods bein manufctured using the macine.
The upgrade also increased the estimated remaining life of the machine at
1 October 2007 to machine hours and its estimate residual vlue was revised to
40000. What is the depreciaton expense in 2007?
(A)180000 (B)270000 (C)119000 (D)250000

答：C

我的作法：
機器成本=1050000*0.8*0.95+30000+28000+22000=878000
折舊：
2005/10/1~2006/9/30=(878000-20000)*1200/6000=171600
2006/10/1~2007/9/30=(878000-20000)*1800/6000=257400
2007/10/1之BV=878000-171600-257400+200000=649000
2007/10/1~2008/9/30=(649000-40000)*850/4500=115033

2007之折舊=257400*9/12+115033*3/12=221808

請問版上的高手，我錯在哪裡？ 算好久數字都不對= =

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