Simple Interest Because simple interest is used on short-term notes, the time period is often given in days rather than months or years. We convert this to years by dividing by 360, assuming a 360 day year called a banker's year. Question 1 9.09 pts Use a banker's year described above to answer this question. T-bills (Treasury bills) are one of the instruments the U.S. Treasury Department uses to finance public debt. If you buy a 280-day T-bill with a maturity value of $11,750 for $11,382.87, what annual simple interest rate will you earn? Express your answer as a percentage. %. Round to the nearest thousandths of a percent (3 decimal places)