$($Calculating an annuity$$s interest rate$)$ Your folks would like some advice from you. An insurance agent just called and offered them the opportunity to purchase an annuity for $$21,074\mathrm{.}25$ that will pay them $$3,000$ per year for $20$ years. They don$$t have the slightest idea what return they would be making on their investment of $$21,074\mathrm{.}25.$ What rate of return would they be earning? Use basic formula and be precise. No excel.