If straight-line depreciation is used, the value being depreciated over 8 years is
25,560 -3,000 = 22,560
so the depreciation in 4 years is
22,560*4/8 = 11,280
This is also the remaining value to be depreciated, now in 2 years. The depreciation in year 5 is
11,280/2 = 5,640