E-Sharp Company purchased tool sharpening equipment on July 1, 2006, for $97,200. The equipment was expected to have a useful life of three years, or 22,800 operating hours, and a residual value of $6,000. The equipment was used for 3,650 hours during 2006, 8,000 hours in 2007, 7,850 hours in 2008, and 3,300 hours in 2009.

Instructions
Determine the amount of depreciation expense for the years ended December 31, 2006, 2007, 2008, and 2009, by
(a) The straight-line method,
(b) The units-of-production method,
(c) The double-declining-balance method.