A car dealer will sell you a used car for $8,734 with $734 down and payments of $384.67 per month for 24 months. What is the simple interest rate? (Round each answer to the nearest tenth.)

384.67 * 24 = 9,232.08

9,232.08 - 8,000 = 1,232.08

1,232.08 / 8,000 = 0.15401 = 15.4%