Compute the payback period for each of these two separate investments: a. A new operating system for an existing machine is expected to cost $270,000 and have a useful life of five years. The system yields an incremental after-tax income of $77,884 each year after deducting its straight-line depreciation. The predicted salvage value of the system is $10,000. b. A machine costs $200,000 has a $14,000 salvage value is expected to last eight years: and will generate an after-tax income of $43,000 per year after straight-line depreciation