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On January 2. 2018, Country Lumber installed a computerized machine in its factory at a cost of $168,000. The machine's useful life was estimated at four years or a total of 190,000 units with a $35,000 trade-in value. Country Lumber's year-end is December 31. Calculate depreciation for each year of the machine's estimated useful life under each of the following methods: a. Straight-line b. Double-declining-balance C. Units-of-production, assuming actual units produced were: Year................."."" 2018 2019 2020 2021 Units................... 39,900 43.550 54.200 72.000