Plummer Industries purchased a machine for $39,000 and is depreciating it with the straight line method over a life of 8 years, using a residual value of $2,200. At the beginning of the sixth year, an extraordinary repair was made costing $6,400, the estimated useful life was extended to 13 years, and no change was made to the estimated residual value. Calculate depreciation expense for year 6.what is depreciation expense?