A par value of 1000 yuan bonds, half a year nominal interest rate of 6%, can be issued in the fifth year after the beginning of advance redemption at par value, in early redemption terms, to ensure that half a year nominal yield of 7% of the price issued.  If you were to redeem it at maturity, in order to still get a 7% yield, you'd redeem it at 1,000 plus X.  The calculation of X.