Waylander Coatings Company purchased waterproofing equipment on January 6, 2015, for $320,000. The equipment was expected to have a useful life of four years, or 20,000 operating hours, and a residual value of $35,000. The equipment was used for 7,200 hours during 2015, 6,400 hours in 2016, 4,400 hours in 2017, and 2,000 hours in 2018.

1. Determine the amount of depreciation expense for the years ended December 31, 2015, 2016, 2017, and 2018, by (a) the straight-line method, (b) the units-of-output method, and (c) the double- declining-balance method. Also determine the total depreciation expense for the four years by each method.