Martin Corporation acquired a truck on January 1, 2016, at a cost of $84,000. The truck was originally estimated to have a salvage value of $4,000 and an estimated useful life of 8 years. Depreciation had been recorded through December 31, 2018, using the straight-line method. On January 1, 2019, the estimated salvage value was revised to $6,000, and the useful life was revised to a total of 7 years. Required: (Show all calculations) a. Calculate the annual depreciation expense for the years 2016 through 2018. (2 marks) b. Calculate the book value of the truck at December 31, 2018. (3 marks) c. Calculate the depreciation expense per year after revision. (3 marks) d. If the truck is sold at a gain, how is the statement of financial position affected? (2 marks)