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Layton Company purchased tool sharpening equipment on October 1, 2012, for $108,000. The equipment was expected to have a useful life of three years, or 12,000 operating hours, and a residual value of $7, 200. The equipment was used for 1, 350 hours during 2012, 4, 200 hours in 2013, 3, 650 hours in 2014, and 2, 800 hours in 2015. Determine the amount of depreciation expense- for the years ended December 31, 2012, 2013. 2014, and 2015, by (a) the straight-line method, (b) the units-of-output method, and (c) the double-declining-balance method