A tractor for over the road hauling is purchased for $ 90,000. It is expected to be of use to the company for 6 years, after which it will be salvaged for $ 4,000. Calculate the depreciation deduction and the unrecovered investment during each year of the tractors life

a. use straight line depreciation

b. Use declining balance depreciation sing a rate that ensures the book value equals the salvage value

c.Use double declining balance depreciation

d.Use double declining balance switching to straight line depreciation