[CFA入门] 请教level 1 notes上book1的一道题 payment, annuity, investor, received, discount

gracelian

题目如下：

 

An investor will receive an annuity of $4000 a year for ten years. The first payment is to be received five years from today. At a 9% discount rate, this annuity's worth today is closest to:

 

a) $16,684

b) $18,186

c) $25,671

 

应该选哪个？

gracelian

我算出来是a,可是答案给的是b，为什么啊