A factory machine was purchased for $378000 on January 1 , 2021. It was estimated that it would have a $70000 salvage value at the end of its 5 -year useful life. It was also estimated that the machine would be run 40000 hours in the 5 years. The company ran the machine for 4200 actual hours in 2021 . If the company uses the units-of-activity method of depreciation, the amount of depreciation expense for 2021 would be $64680.$39690$70000$32340