Problem 7-1. Pemberton Corporation purchased a machine costing $300,000 that had an estimated use- ful life of six years and residual value of $18,000. The machine is expected to produce 3,525,000 units during its useful life, as follows: Year 123456 Units 930,000 800,000 580,000 500,000 415,000 300,000 3,525,000 Required a. What will be each year's depreciation charge if Pemberton uses the units-of- production method? b. Will this give significantly different depreciation charges in each year than the sum- of-the-years' digits method?