=a. What is the mean net present value (NPV) of the project? (Hint: The NPV (rate, cash stream) function in Excel returns the NPV of a stream of cash flows assumed to start one year from now. For example, NPV(10%, C5:F5) returns the NPV at a 10% discount rate when C5 is a cash flow at the end of year 1, D5 at the end of year 2, E5 at the end of year 3, and F5 at the end of year 4.)