问题如下：
What is the cash price of the Treasury bill that lasts for 200 days and has a quoted price of 4.12?
解释：
The cash price per USD 100 of face value is
100 - (200/360) x 4.12 = 97.7111
课上老师讲说t bond的cash price是cash price=quoted price+accrued interest T bill 的公式是cash price=100-（quoted price*n/360) 想问一下为什么两个公式里一个是加一个是减呢？而且这样看的哈tbond应该总是大于100，而t bill会总是小于100 谢谢