Thornton Industries purchased a machine for $50,000 and is depreciating it with the straight-line method over a life of 10 years, using a residual value of $ 3,400 . At the beginning of the sixth year, an extraordinary repair was made costing $4,800, 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.