Suppose $1-$year Treasury bonds yield $4\mathrm{.}00\%$ while $2-$year T$-$bonds yield $4\mathrm{.}80\%.$ Assuming the maturity risk premium for T$-$bonds is zero, what is the yield on a $1-$year T$-$bond expected to be one year from now?

A$.5\mathrm{.}81\%$

B$.4\mathrm{.}38\%$