On January 1, 2016, Canseco Plumbing Fixtures purchased equipment for $50,000. Residual value at the end of an estimated four-year service life is expected to be $8,000. The company expects the machine to operate for 15,000 hours. The machine operated for 3,200 and 4,000 hours in 2016 and 2017, respectively.

a.	Calculate depreciation expense for 2016 and 2017 using straight line method.

b.	Calculate depreciation expense for 2016 and 2017 using sum-of-the-years'-digits method.