问题如下：
An annual coupon bond with a 5% coupon rate has a yield-to-maturity of 7%, and there are four years to its maturity from now. The estimated price value of a basis point for the bond is:
选项：
A.0.0078.
B.0.0325.
C.0.0569.
解释：
B is correct.
If the YTM decreases by 1bp, the price of the bond is:
PMT = 5, FV=100, I/Y=6.99%，N=4 ，CPT → PV = - 93.258
If the YTM increases by 1bp, the price of the bond is:
PMT = 5, FV=100, I/Y=7.01%，N=4 ，CPT → PV = - 93.193
PVBP of the bond is:
[(PV-) - PV(+)]/2 = 93.258 - 93.193 / 2 =0.0325
这题怎样计算？
