(a)$813.65

Working: -(Purchase price)+$35*PVIFA(n=13, i=5.55%)+$1,000*PVIF(n=13, i=5.55%)=0

（由于alyson已经收取了2年*$35，所以n=15-2=13）

-(Purchase price)+$35*9.090105+$1,000*0.495499=0

解方程得：Purchase price=$813.65

(b)0.5018%

Working: -875.02228170591+$35*PVIFA(n=2, i=?)+$813.65*PVIF(n=2, i=?)=0

使用插值法解方程：

假设i=0.5%, NPV=-875.02228170591+$35*PVIFA(n=2, i=0.5%)+$813.65*PVIF(n=2, i=0.5%)=

-875.02228170591+$35*1.985099+$813.65*0.990075=0.0307

假设i=1%, NPV=-875.02228170591+$35*PVIFA(n=2, i=1%)+$813.65*PVIF(n=2, i=1%)=

-875.02228170591+$35*1.970395+$813.65*0.980296=-8.4406

i=0.5%+(1%-0.5%)*0.0307/(0.0307-(-8.4406))=0.5018%