An asset was purchased on January 1 for $80,000 with an estimated residual value of $20,000 at the end of its useful life. The current year's Depreciation Expense is $10,000 calculated on the straight-line basis and the balance in the Accumulated Depreciation account at the end of the year is $20,000. The remaining useful life of the asset is O 10 years. 4 years. O 6 years. O 2 years