Compute the payback period for each of these two separate investments (round the payback period to two decimals):
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. The 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.