$($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 $$22,110\mathrm{.}21$ that will pay them $$3,500$ per year for $10$ years, but they don't have the slightest idea what return they will be making on their investment of $$22,110.21.$ What rate of return will they be earning?

The annual rate of return they will be earning is

$\%.($Round to two decimal places.$)$