Problem $2-21($LG $2-8)$

Assume the current interest rate on a one$-$year Treasury bond $($R$11)($R$11)$ is $4\mathrm{.}78$ percent, the current rate on a two$-$year Treasury bond $($R$21)($R$21)$ is $5\mathrm{.}53$ percent, and the current rate on a three$-$year Treasury bond $($R$31)($R$31)$ is $6\mathrm{.}78$ percent. If the unbiased expectations theory of the term structure of interest rates is correct, what is the one$-$year interest rate expected on Treasury bills during year $3($ E$($r$13)$E$($r$13)=$ or f$13$f$13)?$

Note: Do not round intermediate calculations. Round your percentage answer to $2$ decimal places $($e$.$g$.,32\mathrm{.}16).$