The prevailing interest rate is 5% over the first year and 10% over the second year.
That is, over 2 years, your interest rate is (1 + 5%) . (1 + 10%) - 1 = 15.5%.
Your project costs $1,000 and will pay $600 in the first year and $500 in the second year. What does the IRR rule recommend? What does the NPV rule recommend?