On January 2, 2018, Archer Company, a skateboard manufacturer, installed a computertzed machine in its factory at a cost of $168,000. The machine's useful life was estimated at four years or a total of 180,000 units with a $24,000 trade in value. Archer Company's year-end is December 31 Calculate depreciation for each year of the machine's estimated useful life under each of the following methods: (Do not round intermediate calculations.) a. Straight-line b. Double-declining-balance c. Units-of-production, assuming actual units produced were: Year 2018 2019 2020 2021 Units 39,700 43,250 54,000 70,000 2018 $ 31, Extensions 34,600 2019 43,200 2020 56,000 2021 Total $ $ $ $ $ 36,000 36,000 $ 36,000 $ 36,000 $ 144,000 84,000 $ 42,000 $ 24,000 $ 0 $