$18.$ An investor bought a bond for $$842\mathrm{.}24$ and sold it $3$ years later for $$855\mathrm{.}21$ after receiving their $6$th semi$-$annual coupon payment of $$45.$ What was the investor's effective annual return on this investment?

Enter rate in decimal form rounded to the fourth digit, as in $"0\mathrm{.}1234"$