hello! please help me to understand these :) thank you!

6) A project costs $1000 and generates cash inflows of $800 for 3 years. If its required return is 15% what is its payback period? Round to 2 decimal places. 7) A project costs $1000 and generates cash inflows of $800 for 3 years. If its required return is 15% what is its IRR? Round to 2 decimal places