Norman Rentals can purchase a van that costs $78,000; it has an expected useful life of three years and no salvage value. Norman uses straight-line depreciation. Expected revenue is $39,221 per year. Assume that depreciation is the only expense associated with this investment. Required Determine the payback period. (Round your answer to1 " decimal place.) ck pe years b. Determine the unadjusted rate of return based on the average cost of the investment. (Round your answer to 1 decimal place. (i.e., 234 should be entered as 23.4).)