THe one to $5$ year spot rates are $2\%,3\%,4\%...\mathrm{.}6\%$ respectivly. You expect that the spot curve will stay the same for the next $2$ years. Then if you buy a $4$ year maturity, $6\%$ coupon bond today and hold it for $2$ years $($reinvesting the t$=1$ coupon$)$ your annualized return is what