An investor wants to find the duration of$$ a$($n$)30-$year, $8\%$ semiannual$$ pay, noncallable bond$$ that's currently priced in the market at $$$$896\mathrm{.}81,$ to yield $9\%.$ Using a $250$ basis point change in$$ yield, find the effective duration of this bond $($Hint$$: use Equation$11\mathrm{.}11).$