please assist to detail in step so i can learn for IRR

Internal rate of return (IRR) (1) A contract has an NVP of $10,000 with a required rate of return of 12% but an NPV of $5,000 with a return of 16%. Use linear interpolation to find the approximate internal rate of return. (2) A contract has an NPV of $5,000 with a required rate of return of 10% and an internal rate of return of 12%. Using linear interpolation, what would be the approximate NPV if the required rate of return was reduced to 8%