Atlantic Airlines purchased an aircraft on January 1, 2015, at a cost of $45,000,000. The estimated useful life of the aircraft is 20 years, with an estimated residual value of $5,000,000. On January 1, 2018 the airline revises the total estimated useful life to 13 years with a revised residual value of $4,000,000 Instructions (a) Compute the depreciation and book value at December 31, 2017 using the straight-line method and the double-declining balance method. (b) Assuming the straight-line method is used, compute the depreciation expense for the year ended December 31, 2018