44. A machine which cost $500,000 is acquired on October 1, 2020. Its estimated salvage value is $50,000 and its expected life is six years. Round all answers to the nearest dollar. a. Calculate depreciation expense for 2020 and 2021 using the straight-line method. b. Calculate depreciation expense for 2020 and 2021 using the double-declining balance method. c. Calculate depreciation expense for 2020 and 2021 using the sum-of-the-years'-digits method