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Diana Company purchased a machine on January 1, 2019, for $100,000, with a 5-year life, and a $10,000 residual life. What is the book value of the machine on December 31, 2021, if the company uses the double- declining balance method of depreciation? Select one: a. $21,600 b. $14,400 C. $36,000 d. $14,400