Compute the payback period for each of these two separate investments: a. A new operating system for an existing machine is expected to cost $520, 000 and have a useful life of six years. The system yields an incremental after-tax income of $150, 000 each year after deducting its straight-line depreciation. predicted salvage value of the system is $10, 000. b. A machine costs $380, 000, has a $20, 000 salvage value, is expected to last eight years, and will generate an after-tax income of $60, 000 per year after straight-line depreciation