问题如下：
Suppose that a country in Australia issued a 15-year capital-indexed bond which had a link to the Consumer Price Index(CPI). The par value was 2,000 and the coupon rate was 6%. The way of the interest paid by the bond was semi-annually. Assuming that the bond was issued in half a year ago, today’s CPI is decreased by 5%. So, in today, which of the following best describes this bond?
选项：
A.The principal repayment decreases to 1,950.
B.The first coupon payment of the bond is 57.
C.The coupon rate of the bond decreases to 5.7%.
解释：
B is correct.
According to the concept of the capital-indexed bond, although the coupon rate will not change, the coupon payment will change with the increase or decrease of the principal amount which depends on the increase or decrease of the index. We can know that the CPI decreases by 5%, it leads to the principal amount also decreases by 5% which is 2,000 x (1 – 0.05) = 1,900. Although the coupon rate will not change which is 6%, the first semi-annual coupon payment is (1,900 x 0.06) / 2 = 57 with the use of the new principal amount.
这道题能做对，想问一下这种情况下将来归还的本金是2000还是1900？
