Green Garden Company Purchased a Tractor at a Cost of $240,000

Green Garden Company purchased a tractor at a cost of $240,000 on January 1, 2015. The tractor has an estimated residual value of $40,000 and an estimated life of 8 years. At the end of two years of service, Green Garden Co. reevaluated the tractor's useful life. Management extended the useful life an additional four years, but estimated that the tractor would have no residual value at the end of this time.
If the company uses straight-line depreciation, what amount would be recorded as the depreciation expense each year, beginning with the third year?

A) $19,000
B) $15,000
C) $25,000
D) $15,834