In 2006, a man mailed a $100 check to another man to repay a $100 debt of his great-great-grandfather, who died in 1878. A bank estimated the interest on the loan to be $216 million for the 128 years it was due. Find the interest rate the bank was using, assuming interest is compounded annually The bank was using an interest rate of %(???)
(Do not round until the final answer. Then round to the nearest hundredth as needed.)