The Camino Real Landfill was required to install a plastic liner to prevent leachate from migrating into the groundwater. The fill area was 50,000 m^2 and the installed liner cost was exist8 per m^2. In order to recover the investment, the owner charges to unload at the rates of exist10 per pickup, exist25 per dump truck, and exist70 per compactor truck load. The fill area is adequate for 4 years. If the annual traffic is estimated to be 2500 pickup loads, 650 dump-truck loads, and 1200 compactor-truck loads, what rate of return will the landfill owner make on the investment? The rate of return that will be made by the landfill owner is % per year