they say the answer is $70000, but im not sure how they got this. Can you plesse explain and work through the solution?

13. On January 1,2018 , Rhino Corp. purchased a machine for $850,000. The machine was being depreciated using the straight-line method over an estimated useful life of eight years, with a $50,000 residual value. At the beginning of 2023 , the company determined that the machine's useful life was underestimated, it should have been 10 years; however, this would result in $0 residual value. The depreciation expense for 2023 should be a) $70,000 b) $80,000. c) $63,750. d) $85,000