A $30-$year bond with annual $10\%$ coupons is priced at $120\%$ of par.

It is callable at the following dates and prices:

Call Date $($Years from now$)$ Call Price $(\%$ of Par$)$

$1-10125\%$

$11-15120\%$

$16-20115\%$

$21-29105\%$

If the bond is not called, it will redeem for par.

Determine the annual effective yield that a purchaser is guaranteed to attain at the current price