DDB加速折旧法不用减去Salvage value的原因

问题如下：

Michael's factory purchased a machinery for production at £50,000 at the end of year 2016. The machinery has an estimated useful life of 5 years and an estimated salvage value of £5,000. If the machinery produces 20,000 units of products in year 2017 and the total production of its whole life is expected to be 80,000 units. How does Michael report depreciation of machinery using the double-declining balance method and the units-of-production method?

选项：

解释：

A

Double-declining balance: depreciation in year 1= 2/ asset life*book value at the beginning of 2017=2/5*£50,000=£20,000.

Units-of-production: depreciation in year 1=(cost-salvage value)/ total production* units produced in year 2017=£(50,000-5,000)*20,000/80,000=£11,250.