Exercise 5: A machine is purchased for 180,000 in year 1. It is estimated to have a residual value of 20,000 at the end of its estimated useful life of 8 years. The depreciation policy of the company is to depreciate such machinery on a straight-line basis over its estimated useful life. (a) Calculate the depreciation charge and net book value each year on the basis of the information given above. (b) Recalculate the depreciation charge and net book value each year on the assumption that the asset's life is only 5 years and the residual value is only 14,000