问题如下图：
选项：
A. 
B. 
C. 
解释：
Shame to ask this very basic question... but need to get it clarified.
for annualized interest rate shown in the case, why use 0.066% * 180/360?
is (1+0.066%) = (1+ 6month interest rate) (1+6month interest rate)?
then why not using (1+0.066%)^1/2 -1 ?
