Perdue company purchased equipment on April 1 for $104,220. The equipment was expected to have a useful life of 3 years, or 8,100 operating hours, and a residual value of $2,970. The equipment was used for 1,500 hours during year 1, 2,800 hours in year 2, 2,400 hours in year 3, and 1,400 hours in year 4.

Which of the following depreciation methods would be most appropriate for Perdue company to use for this equipment?
a) Straight-line depreciation
b) Double-declining balance depreciation
c) Units of production depreciation
d) Sum-of-the-years'-digits depreciation