The heat loss through the exterior walls of a processing plant is expected to cost the owner $3000 next year. A salesman from Superfiber, Inc. claims he can reduce the heat loss by 80% with the installation of $15000 worth of Superfiber now. If the cost of heat loss rises by $ 200 per year, after next year (gradient), and the owner plans to keep the building 10 more years, what is his rate of return, neglecting depreciation and taxes? To determine the rate of return, try a trial value 12%: NPW= [Select] Then a [Select ] interest rate should be tried, in order to find the correct rate of return