Company A had purchased machinery 3 years ago at the beginning of 2013 and depreciated it using the straight-line depreciation method until the end of 2015. Subsequent to year end Company A determined that the useful life of the machinery was going to be a total of 7 years rather than the 5 years they originally estimated. The machinery was originally purchased for $30,000 and had a $3,000 estimated initial residual value. In addition to the useful life now being a total of 7 years, the residual value has been revised to an estimated $1,200. Calculate the original annual depreciation expense prior to the revision in estimates. The original annual depreciation $ 5400 year