在ASM 237页。题干是
A senior executive is offered a buyout package by his company that will pay him a monthly benefit for the next 20 years. Monthly benefits will remain constant each of the 20 years. At the end of each 12-month period, the monthly benefits will be adjusted upwards to reflect the percentage increase in the CPI. You are given
(i) The first monthly benefit is R and will be paid one month from today
(ii) The CPI increases 3.2% per year forever.
At the annual effective interest rate of 6%, the buyout package has a value of 100,000. Calculate R.

这道题的答案是548，答案给的解题方法我也明白.
但是如果我用我的方法，
先算adjusted interest rate=1.06/1.032-1=0.0271
再用2.71【I/Y】20【N】100,000【PV】【CPT】【PMT】算得-6544.60，即第一年付款总额然后算出月利率1.06^(1/12)=1.0049
然后再用6544.60【FV】0.49【I/Y】12【N】【CPT】【PMT】，结果为什么是530

请问我的步骤有哪里错了吗？谢谢指教！