问题如下：
Assuming that the yield falls by 90 basis points, what's the convexity effect for a bond with a convexity of 120?
选项：
A.0.972%
B.0.486%
C.1.080%
解释：
B is correct.
Correct answer:
convexity effect= (1/2) * convexity * (ΔYTM)2 = (0.5)(120)(0.009)2=0.00486=0.486%
Incorrect answer:
convexity effect= convexity * (ΔYTM)2 = (120)(0.009)2=0.00972=0.972%
convexity effect= convexity * (ΔYTM) = 120 * 0.009 =1.08%
老师，也就是按照公式来分析的话，无论yield的变化是涨还是跌，convexity effect后的price变化均为正对吧？因为公式中YTM是平方，是吗？谢谢
