On January 1, 2018, Canseco Plumbing Fixtures purchased equipment for $38,000. Residual value at the end of an estimated four-year service life is expected to be $2,000. The company expects the machine to operate for 10,000 hours. The machine operated for 2,600 and 3,400 hours in 2018 and 2019, respectively. a. Calculate depreciation expense for 2018 and 2019 using straight line method. b. Calculate depreciation expense for 2018 and 2019 using sum-of-the-years'-digits method. c. Calculate depreciation expense for 2018 and 2019 using double-declining balance method. d. Calculate depreciation expense for 2018 and 2019 using units-of-production method (using machine hours).