A municipality intends to install a system of regulation of luminous flux for the public lighting. The initial investment will be 20482.50 for the purchase of the equipment and 2,500 is required for installation. The investment will have the support of an European found program that will give 50% of the initial investment. It is also necessary 18871.10 for the contracting of some external services and 4861.00 will be supportedby the European program. The local authority will have to carry out a maintenance contract with the supplier company for which it willpay 2500 / year. Knowing that the system will allow the reduction of the annual energy bill by 20991.50, that its useful life will be 10 years and considering a = 5%, calculate: a) Payback b) Net PresentValue(NPV) c) Internal rateof return(IRR).