这里表达觉得迷惑

问题如下：

Which forward rate cannot be computed from the one-, two-, three-, and four-year spot rates? The rate for a:

选项：

one-year loan beginning in two years.

two-year loan beginning in two years.

three-year loan beginning in two years.

解释：

C is correct.

There is no spot rate information to provide rates for a loan that terminates in five years. That is f(2,3) is calculated as follows:

$f(2,3)=\sqrt[3]{\frac{\lbrack{1+r(5)}\rbrack}{{\lbrack{1+r(2)}\rbrack}^2}^5}-1$

The equation above indicates that in order to calculate the rate for a three-year loan beginning at the end of two years you need the five year spot rate r(5) and the two-year spot rate r(2). However r(5) is not provided.

考点：Forward rate与Spot rate

由f(2,3)的公式可知，如果要计算f(2,3)，我们需要知道五年期的即期利率r(5)以及两年期的即期利率r(2)。然而题目中没有给出五年期的即期利率r(5)，所以f(2,3)无法得到。