Prepare journal entries for the following transactions: a. A machine that cost $10,000 with a residual value of $2,000 is fully depreciated and discarded. b. A machine purchased on January 1, 2020 for $20,000, with a useful life of 4 years, and a residual value of $4,000, is sold on April 1, 2020 for $8,000. Use the straight-line method. c. A machine that cost $15,000, has accumulated depreciation of $12,000 is sold for $5,000.