depreciation expense

Gates Co. purchased machinery on January 2, 2007, for $660,000. The straight-line method is used and useful life is estimated to be 10 years, with a $60,000 salvage value. At the beginning of 2013 Gates spent $144,000 to overhaul the machinery. After the overhaul, Gates estimated that the useful life would be extended 4 years (14 years total), and the salvage value would be $30,000. The depreciation expense for 2013 should be a) $42,375 b) $55,500 c) $51,750 d) $60,000