A 15-year annuity provides $100 per year for the first five years, $120 per year for the next five years, and $140 per year for the next five years. The annuity is payable at the beginning of each year for the first five years and semiannually at the beginning of each six-month period thereafter. The nominal annual rate of interest is 6%, compounded semiannually. Calculate the purchase price of this annuity.