A firm is considering using either straight-line depreciation or 3-year MACRS to depreciate a $500,000 asset purchased today. The asset will be used for 4 years and will have no salvage value. If the firm's cost of capital is 10%/year, and their tax rate is 21%/year, how much will NPV be improved by using MACRS versus straight-line? To solve this question, calculate the depreciation tax shield (annual deprecation * tax rate) for each year for both methods, then calculate