In early 2014, a company purchased $35,500 worth of office equipment with an estimated useful life of 7 years and an estimated residual value of $ 4,000 .The company used the straight-line method of depreciation for all office equipment. At the beginning of 2017, they revised its estimated of the useful life of the office equipment to a total of 9 years with a residual value of $2,500. The 2017 depreciation expense is: