The compound interest formula is given by A = P(1+) where A is the accumulated amount, after an initial investment of P dollars is invested for t years, at annual interest rate r, compounded n times per year. Use the formula above to determine how long it will take an initial investment of $5,500 to grow to $16,500, if the account earns 9.3% interest per year, compounded monthly. Round the solution to two decimal places. The account balance will reach $16,500 after years.