Perdue Company purchased equipment on April 1 for $86,670. The equipment was expected to have a useful life of three years, or 6,480 operating hours, and a residual value of $2,430. The equipment was used for 1,200 hours during Year 1, 2,300 hours in Year 2, 1,900 hours in Year 3, and 1,080 hours in Year 4. Required:

Determine the amount of depreciation expense for the years ended December 31, Year 1, Year 2, Year 3, and Year 4, by:

a. the straight-line method
b. units-of-output method.
c. the double-dedining-balance method.