A financial planning service offers a college savings program. The plan calls for you to make six annual payments of $$13,500$ each, with the first payment occurring today on your child$$s $12$th birthday. Beginning on your child$$s $18$th birthday, the plan will provide $$27,000$ per year for four years. What return is this investment offering? $($Do not round intermediate calculations and enter your answer as a percent rounded to $2$ decimal places, e$.$g$.,32\mathrm{.}16.$