$($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 $$$$16$ comma $954\mathrm{.}15$ that will pay them $$$$3$ comma $500$ per year for $10$years$,$ but they$$ don't have the slightest idea what return they will be making on their investment of $$$$16$ comma $954\mathrm{.}15.$ What rate of return will they be$$ earning?