Marshall Company purchases a machine for $200,000. The machine has an estimated residual value of $40,000. The company expects the machine to produce four million units. The machine is used to make 420,000 units during the current period If the units-of-production method is used, the depreciation expense for this period is: Multiple Choice 0 $420,000 $380,000 o $16,800 o o $21,000