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).)Norman Rentals can purchase a van that costs $144,000; it has an expected useful life of four years and no salvage value. Norman uses straight-line depreciation. Expected revenue is $59,544 per year. Assume that depreciation is the only expense associated with this investment.