For the following set of cash flows, Year 0 1 2 3 Cash Flow -$6,800 7,000 4,600 3,500 a. What is the NPV at a discount rate of O percent? b. What is the NPV at a discount rate of 12 percent? c. What is the NPV at a discount rate of 18 percent? d. What is the NPV at a discount rate of 23 percent