A company is considering two mutually exclusive projects, M and N. Project M requires an investment of $3,000 and has annual cash flows of $1,200 for 4 years. Project N costs $2,500 and provides cash flows of $1,000, $1,200, $1,300, and $1,400 over 4 years.

1. Calculate the NPV of each project with a discount rate of 6%.
2. Determine the IRR for both projects.
3. Compare the payback periods of the two projects.
4. Decide which project is preferable based on the profitability index.