On January 1, 2014, a machine costing $230,000 with a 4-year service life and an estimated $3,000 residual value was purchased. It was also estimated that the machine would produce 50,000 units during its life. The actual units produced during its first 2 years of operation were 9,000 and 10,000 respectively. Calculate the amount of depreciation expense for calendar years 2014 and 2015 under each of the following assumptions: