(Annuity interest rate) Your parents 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 $14,217.56 that will pay them $2,500 per year for 20 years. They do not have the slightest idea what return they would be making on their investment of $14,217.56. What rate of return would they be earning? (Round to two decimal places.)