问题如下：
What is a forward rate agreement? Explain how it is usually settled.
选项：
解释：
A forward rate agreement (FRA) is an agreement to exchange
(a) An amount obtained when a pre-determined fixed rate of interest is applied to a certain principal for a certain future period, and
(b) An amount obtained when the actual (floating) rate observed in the market is applied to the same principal for the same period.
An FRA is normally settled at the beginning of the underlying period. The settlement amount is the difference between the two interest amounts discounted from the end of the period to the beginning of the period at the floating rate.
老师能翻译一下答案的英文吗
