(Solving for r in an annuity) Your folks just called and would like some advice from you. An insurance agent just called them and offered them the opportunity to purchase an annuity for $19,834.50 that will pay them $2,500 per year for 15 years, but they don't have the slightest idea what return they will be making on their investment of $19,834.50. What rate of return will they be earning? The annual rate of return they will be earning is \%. (Round to two decimal places.)