3. A proposed project has the following expected cash flows: Year Cash Flow $100 50 740 40 Please calculate the payback and NPV at a required return of 12 percent. 4. Amazon's stock prices at the end of each the last four months from April to July were: 231.90,212.91, 228.35, and 233.30. Amazon does not pay dividends. Please calculate the monthly rate of return for the stock for May to July, the average monthly rate of return for these three months, and standard deviation of monthly rate of return