On March 1, 2018, Ranger Company purchased a piece of equipment with a list price of $75,000. Estimated useful life of the equipment is 5 years. The salvage value of the equipment is estimated to be $5,000. Requirements: Calculate the 2018, 2019 and 2020 depreciation expense under the following methods: Straight line Double-declining balance What is the book value of the equipment on December 31, 2020 using both depreciation methods? Briefly discuss the rationale for the straight line and the double declining balance methods of depreciation. Include in your discussion what factors should be considered in determining the useful life of an asset.