For the nonconventional net cash flow series shown, the external rate of return per year using the MIRR method, with an investment rate of 20% per year and a borrowing rate of 8% per year, is closest to: For the nonconventional net cash flow series shown, the external rate of return per year using the MIRR method, with an investment rate of 20% per year and a borrowing rate of 8% per year, is closest to