一條百分數~easy...(複利息)

小明月初向財務公司借款$20000, 年利率24%, 每月計算複利息。如果他每個月月底還款$5000, 問還款4次後他還欠財務公司多少錢?
Let 欠款 be $b4

1st month balance (b1) =
[20000 * (1 + 24/12%) - 5000] =
15400

2nd month balance (b2) =
[b1 * (1 + 24/12%) - 5000] =
[15400 * (1 + 24/12%) - 5000] =
10708

3rd month balance (b3) =
[10708 * (1 + 24/12%) - 5000] =
5922.16

4th month balance (b4) =
[b3 * (1 + 24/12%) - 5000] =
[5922.16 * (1 + 24/12%) - 5000] =
1040.60

Ans. 小明還欠財務公司 $1040.60

28000

$28000

[[20000*(1+24%/12)-5000]*(1+24%/12)-5000]1+24%/12)-5000]1+24%/12)-5000]
=20000

2006-10-21 20:00:10 補充：
應該係28000呀___sor

還款4次後他還欠財務公司=28000