4. A farmer bought a new harvester for $100,000. The harvester's operating expenses averaged $10,000 per year, but the machine saved $40,000 per year in labor costs. It was depreciated over a life of 5 years using the DDB method, assuming a salvage value of $20,000. Given an income tax rate of 30% and a MARR rate of 5%, determine the after-tax net present worth of this investment. Year Depreciation (DDB) Depreciation (SL) Book Value 4 ear BTCF Depreciation Taxable Income Tax ATCF 4