请问一级习题集第507、528、561看不懂答案 574为何mean renversion，naturel gas parices are negatively correlated。 584如何判定gamma正负，图像gamma无论in at or out of the money不是永远为正吗？

Your supervisor is an expert in market and credit risk. He recruits you to manage the operational risk department. He would like to use VaR to measure the firm's operational risk and proposes that you use the same VaR framework previously developed for market and credit risk. Which of the following is a valid argument for why it is difficult to estimate an operational VaR using the same framework as market and credit VaR? A.Market risk events are easier to map to risk factors than operational risk events. C.Market and credit VaRs are estimated using only frequency distribution, but operational VaR is estimated using both a freq distribution and a severity distribution. 其他B,D肯定错，但是不明白为什么C错和A对，为什么market risk更容易map to risk factors? 请老师解答一下，谢谢！

老师，这个题中，md应该与y也有关啊。为什么让md相同再判断dv01？

老师，四个选项分别如何解释

老师，这个题怎么解释

A $1000 par corporate bond carries a coupon rate of 6%, pays coupons semiannually, and has ten coupon payments remaining to maturity. Market rates are currently 5%. There are 90 days between settlement and the next coupon payment. The dirty and clean prices of the bond are closest to: A. 1043.76, 1013.76 B. 1043.76, 1028.76 C.1056.73, 1041.73 D.1069.7, 1054.7 在第10期贴现回去那段不太明白，PV=1043.76. 1043.76*1.025(1/2)=1056.73 为什么不是1043.76/1.025（1/2）呢？ 请老师解释下乘除号在这道题目里面的分别，谢谢

老师，这里为什么euro interest rate 是下降才是in the money

The standard VaR calculation for extension to multiple periods assumes that returns are serially uncorrelated. If prices display trends, the true VaR will be: A. The same as the standard VaR. B. Greater than the standard VaR. C. Less than the standard VaR. D. Unable to be determined. 没有想明白这道题，请老师再解释一下

par rate ，spot rate 和yield分别代表什么？

老师，可以解释下利率风险和在投资风险吗？callable和puttable bond在哪种情况下更容易行权？