请问 L3 中 的 before tax required return rate required, return, before, after

zhoule

题目 spending rate 3%, inflation 3%, tax rate 30%, 问你after tax required return rate以及 before tax required return rate
我做的答案是
after tax required return rate=(1+3%)*(1+3%)-1
before tax required return rate=((1+3%)*(1+3%)-1)/(1-30%)
可是我看到的notes里面practise book的答案是
before tax required return rate=3%/（1-30%）+3%
请教notes的这个答案是不是错了？应该查什么资料来证实？