帮我算一个题好吗

suppose that in eight months world university services of canada requires $100,000 to buy trucks. it plans to raise these funds by making monthly deposits into a bank account. over the period, the stated annual interest rate changes: it is 9 percent for first three months, and 12 percent for the next five. if the first four deposits are of $10,000, calculate the constant deposit needed for each of the next four months in order to raise the $100,000

最后结果是14241，高人可以给我讲一下这个结果是怎么得到的吗

设后4个月每月投入为X。
10000乘（1+0.09）*8+10000乘（1.09）*7+10000乘（1.09）*6+10000乘（1.12）*5+X乘（1.12）*4+X乘（1.12）*4+。。。。。X乘（1.12）*1=100，000
算出X。

2# christian18

我不理解你给你公式的意思， 不好意思

就是一系列现金流（其中前几个月是已知的，后几个月是需要求解的）的终值问题，