问题如下图：
接本题callable bond的计算方法，为什么倒推式从第三年年末就触发了行权，还会继续在2时点和1时点继续往前折现计算呢？
选项：
A. 
B. 
C. 
解释：
NO.PZ201712110200000304 问题如下 Baseon the information in Exhibit 1 anExhibit 2, the value of the embeeoption in Bon4 is closest to: A.nil. B.0.1906. C.0.8789. C is correct. Bon4 is a callable bon Value of issuer call option = Value of straight bon– Value of callable bon The value of the straight bonmcalculateusing the spot rates or the one-yeforwarrates.Value of option-free (straight) bonwith a 1.55% coupon using spot rates:1.55/(1.0100)1 + 1.55/(1.012012)2 + 101.55/(1.012515)3 = 100.8789.The value of a callable bon(par) with no call protection periocannot excee100, thprior higher the bonwoulcalle The value of the call option = 100.8789 – 100 = 0.8789. 这道题V-straight_bon一开始是用SPOT RATE，从第三期往前折算（二叉树方法，只是不用分叉计算），发现出来结果是101.1742和答案100.8788不一样。然后我用forwarrate算一次发现结果就是100.8788，由此联想到，请问二叉树中各期利率是不是forwarrate? 我一直理解为SPOT RATE
NO.PZ201712110200000304 问题如下 Baseon the information in Exhibit 1 anExhibit 2, the value of the embeeoption in Bon4 is closest to: A.nil. B.0.1906. C.0.8789. C is correct. Bon4 is a callable bon Value of issuer call option = Value of straight bon– Value of callable bon The value of the straight bonmcalculateusing the spot rates or the one-yeforwarrates.Value of option-free (straight) bonwith a 1.55% coupon using spot rates:1.55/(1.0100)1 + 1.55/(1.012012)2 + 101.55/(1.012515)3 = 100.8789.The value of a callable bon(par) with no call protection periocannot excee100, thprior higher the bonwoulcalle The value of the call option = 100.8789 – 100 = 0.8789. callable bon价格有上限，不能超过100，所以，callable bonvalue应该是100，这句话怎么理解呢
NO.PZ201712110200000304 问题如下 Baseon the information in Exhibit 1 anExhibit 2, the value of the embeeoption in Bon4 is closest to: A.nil. B.0.1906. C.0.8789. C is correct. Bon4 is a callable bon Value of issuer call option = Value of straight bon– Value of callable bon The value of the straight bonmcalculateusing the spot rates or the one-yeforwarrates.Value of option-free (straight) bonwith a 1.55% coupon using spot rates:1.55/(1.0100)1 + 1.55/(1.012012)2 + 101.55/(1.012515)3 = 100.8789.The value of a callable bon(par) with no call protection periocannot excee100, thprior higher the bonwoulcalle The value of the call option = 100.8789 – 100 = 0.8789. embeoption bon以不考虑路径，用forwarrate求价值吗。。。
NO.PZ201712110200000304 问题如下 Baseon the information in Exhibit 1 anExhibit 2, the value of the embeeoption in Bon4 is closest to: A.nil. B.0.1906. C.0.8789. C is correct. Bon4 is a callable bon Value of issuer call option = Value of straight bon– Value of callable bon The value of the straight bonmcalculateusing the spot rates or the one-yeforwarrates.Value of option-free (straight) bonwith a 1.55% coupon using spot rates:1.55/(1.0100)1 + 1.55/(1.012012)2 + 101.55/(1.012515)3 = 100.8789.The value of a callable bon(par) with no call protection periocannot excee100, thprior higher the bonwoulcalle The value of the call option = 100.8789 – 100 = 0.8789. 但是我的疑惑是每次折现用什么数据，答案这里是spot rate进行折现，我却用了额one-yeforwar行折现，就是每次不知道用哪个数字合理？
NO.PZ201712110200000304 问题如下 Baseon the information in Exhibit 1 anExhibit 2, the value of the embeeoption in Bon4 is closest to: A.nil. B.0.1906. C.0.8789. C is correct. Bon4 is a callable bon Value of issuer call option = Value of straight bon– Value of callable bon The value of the straight bonmcalculateusing the spot rates or the one-yeforwarrates.Value of option-free (straight) bonwith a 1.55% coupon using spot rates:1.55/(1.0100)1 + 1.55/(1.012012)2 + 101.55/(1.012515)3 = 100.8789.The value of a callable bon(par) with no call protection periocannot excee100, thprior higher the bonwoulcalle The value of the call option = 100.8789 – 100 = 0.8789. The value of a callable bon(par) with no call protection periocannot excee100, thprior higher the bonwoulcalle为什么不会是小于100呢？没有赎回时间限制的callable bon什么一定价值是100呢？
