資產交換 - 會計

Ferry Corporation follows a policy of a 5% depreciation charge per year.
The following transactions occured in 2007:

March 31,2007:
Negotiations which began in 2006 were completed and a warehouse purchased
1/1/98 (depreciation has been properly charged through December 31,2006) at
a cost of $3,200,000 with a fair market value of $2,000,000 was exchanged for
a second warehouse which also had a fair value of $2,000,000. The exchange had
no commercial substance.Both parcels of land on which the warehouses were
located were equal in value, and had a fair value equal to book value.

Prepare all appropriate journal entries for Ferry Corporation for the above
dates.
解答是
3/31/2007
折舊費用 40,000
累計折舊 40,000

房屋(新) 3,000,000
累計折舊 200,000
房屋(舊) 3,200,000

請問累計折舊的200,000怎麼算的?
我不太懂depreciation has been properly charged through December 31,2006
這句話的意思...
謝謝~

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