According to energysage. com a 3kW solar power system costs $6,571 and has an advertised payback period of 12.11 years (including federal and state incentives, tax credits, and rebates). Assume that the cost savings is equal for each year moving forward and that our required rate of return is 20%. Use each of the methodologies discussed in class to find out if Dr. Brooks should invest in solar panels. Hint: the first step is to calculate the expected annual savings using your knowledge of the payback period. How would this decision change if the appropriate discount rate is 9%