Green Submarine has a four-year project expected to return $6,500 at the end of year 1, $15,000 at the end of year 2, -$2,800 at the end of year 3, and $8,000 at the end of year 4. The discounting rate is 10 percent and the reinvestment rate is 12 percent. The firm needs to spend $20,500 today in order to embark on the project. What is the modified IRR for this project using the combination approach? (Enter your answer as a percent)