this is project management question. please answer both

A financial model used to estimate payback periods can be useful in project selection, however, it may be limited. There is another common tool that can help determine a more realistic payback period, after considering the actual value of present and future investments. What is this tool called? O a Discounted payback period. O b. Realistic rate of return O c.Net present value O d. Return on investment An organization is considering investing in an extensive project initiative. The project will require a hefty investment of $6,216,000, but should help to bring about efficiencies in process improvements across the organization's operations for years to come. In fact, the project is expected to save approximately 574,000 each month after the investment. What is the payback period of this project? a 54 months b. 8.4 years c7 years d. 73 months