MWRR如何计算？

参考这个例题，里面有计算机按法

Suppose, in a given month, the Mientkiewicz account‘s MWR is calculated each week. These MWRs are
•0.021 in week 1•0.0016 in week 2•-0.014 in week 3•0.018 in week 4. The LIRR is obtained by linking these rates:
Answer
CF0 = 400,000; C01 = 0, F01 = 7; C02 = 900,000, F02 = 1; C03 = 0, F03 = 21
C04 = -2,695,398, F04 = 1; CPT (IRR) = 3%
(1+3%)30 – 1 = 142.7%