A plant asset was purchased on January 1 for $64400 with an estimated salvage value of $15000 at the end of its useful life. The current year's depreciation expense is $3800 calculated on the straight-line basis and the balance of the Accumulated Depreciation account at the end of the year is $22800. The remaining useful life of the plant asset is 13 years. 6 years. 17 years. 7 years.