Assume a firm purchases a depreciable asset on January 1, 2018 for $12,000. The asset has an estimated residual value of $2,000, an estimated useful life of 5 years, and uses the straight-line method of depreciation. After 2 years of usage, the firm changes the asset's expected useful life from 5 to 10 years. How much depreciation expense will the firm record on December 31, 2020?