Answer:
2500
Step-by-step explanation:
First depreciate for 6 years using regular method: (Cost - Salvage Value)/Initial Useful life
(50,000-10,000)/8 = 5000 <- this is annual depreciation
For 6 years, $30,000 accumulated depreciation
Now to calculate change in useful life, you do (Cost - Accumulated Depreciation - Salvage Value)/Remaining Useful life
Remaining Useful life = 10-6 = 4
(50,000-30,000-10,000)/4 = 2500