The market portfolio (M) contains the optimal allocation of only risky assets and no risky assets. Let the S1 be the Sharpe ratio of this market portfolio. There exists a risk-free asset. Initially, an investor is fully (100%) invested in M with a portfolio Sharpe ratio of S1. Subsequently, the investor borrows 30% at the risk-free rate, such that she is 130% invested in the market portfolio (M) where this leverage portfolio has a Sharpe ratio of S2. After the leverage (i.e., borrowing at the risk-free rate to invest 30% in M, is the investor still on the efficient frontier and how do the Sharpe ratios? A No (no longer efficient), and S2 < S1. B No, but S2 = S1. C Yes(still efficient), but S2 < S1. D Yes, and S2 = S1. 为什么改变后还在有效前沿上啊

老师，我想请问一下这道题。他问的是下面哪个是潜在的问题。A和我大致能C区分，但是B和D我不太理解，麻烦老师解答一下。这种题目遇到该怎么做呀

老师，这题C、D项怎么理解

cash or nothing put 的定价公式是否为Qe^（-rt）*N（-d2）？

老师，这个ABS在视频里没有细讲啊

为何1说法不对？

当损失率与损失可能正相关的时候 预期损失会增加还是非预期损失会增加？

老师你好，这是习题精讲里的一道题。请问一下C选项错在哪里呀？

I. The convexity of a 10-year zero coupon bond is higher than the convexity of a 10-year, 6% bond. II. The convexity of a 10-year zero coupon bond is higher than the convexity of a 6% bond with a duration of 10 years. 这两句话我很容易搞混，老师可以再讲一下两者差别么，因为都是跟6%的bond比较，但是第二点是duration 10 years，就zero bond小于了

老师这道题求这个月的prepatment是用balance*SMM。但是我用的是SMM=prepament/(balance-scheduled payment)这个公式，scheduled payment是用计算器算的（N=50，I/Y=6/12，PV=-22m，FV=0，摊销得到PRN），算出来答案不对，为什么呢？