Concord Automotive purchased equipment on October 1, 2021, at a total cost of $168,000. The machine has an estimated useful life of 8 years or 100,000 hours, and an estimated residual value of $29,000. During 2021 and 2022, the machinery was used 6,200 and 14,600 hours, respectively. Compute depreciation expense at December 31, 2021 and December 31, 2022, under the following depreciation methods: Straight-line depreciation Units-of-production depreciation $ 2021 2022 $ Double diminishing-balance depreciation $ $