A company purchased equipment for $600,000 which was estimated to have a useful life of 10 years with a salvage or residual value of $20,000 at the end of that time. Depreciation has been recorded for 4 years on a straight-line basis. In 2020 (year 5), it is determined that the total estimated life should be 18 years with a residual or salvage value of $4,000 at the end of that time. What is the net book value a the time of the change? write out the number, include a comma where appropriate, do not include decimals, do not use a dollar sign (i.e. 200,000) What is depreciation expense for 2020