Amer Company purchased a building for $600,000 on January 1, 2018. The estimated residual value is $60,000, and the estimated useful life is 9 years. The straight-line method is used for depreciation. In 2021, Amer Co. changed its estimates to a total useful life of 7 years from the date of purchased and with a salvage value of $75,000. What is 2021 depreciation expense?