Question 4 (10points). Calculate the depreciation expense for the excavator using the units of activity method for year 2007 and 2008. Total machine hours are expected to be 45,000. Actual hours of use in the first three years were: 2007, 15,000 hours; 2008, 12,000 hours; 2009, 10,500 hours. Salvage Value Life In Years Asset Acquired Cost Excavator 1/1/2007 S160,000 15,000