On January 1, 2018, Canseco Plumbing Fixtures purchased equipment for $40,000. Residual value at the end of an estimated four-year service life is expected to be $4,000. The company expects the equipment to operate for 20,000 hours. The equipment operated for 2,700 in 2018. Required: a. Calculate depreciation expense for 2018 using straight line method. b. Calculate depreciation expense for 2018 using double-declining balance method. c. Calculate depreciation expense for 2018 using units-of-production using hours operated.