A plant asset was purchased on January 1 for $60,000 with an estimated salvage value of $12,000 at the end of its useful life. The current year's Depreciation Expense is $6,000 calculated on the straight-line basis and the balance of the Accumulated Depreciation account at the end of the year is $30,000. The remaining useful life of the plant asset is Select one: a. 10 years. b. 3 years. c. 5 years. d. 8 years