请问一下，当曲线upword变平时，代表R下降，这时call option的价值下降，callable band=bond-call option
的价值，所以callable的价值是上升的。
当曲线变陡峭时，代表R上升，put option的价值下降，putable band=bond+put option，所以putable bond价值下降。
以上两种说法是否正确？
在协会的mock中看到这样一段描述：“
as the yield curve flattens, the value of the call option
embedded in Bond A increases. Thus, although the value of Bond A increases, the
increase is partially offset by the increase in the value of the call option.
Therefore, Bond A does not increase as much as the straight bond. As the yield curve
flattens, the value of the put option embedded in Bond B declines because
opportunities for the investor to put the bond decline. Bond B will increase as the
yield curve declines but not as much as the straight bond.
”其中bond A是callable，B是putable。句中的“
the value of the call option
embedded in Bond A increases
”是指call的价值上升还是callable的价值上升？同时这句话的逻辑与上面第一问的逻辑也是不太一样的，还请老师讲解一下，谢谢！
