The Martian Corporation, a space vehicle development company, is starting a new division that will develop the next-generation launch missile engine configuration. Use a hand application of the MIRR method to determine the EROR for the estimated net cash flows (in $1000 units) of $-42,000 in year 0, $11,000 in years 1 through 8, and $-2,000 in year 9. Assume a borrowing rate of 15% and an investment rate of 29% per year. The external rate of return is ________ %.