求解一道数学题！！

Fuckitup

Before being simplified, the instruction for computing income tax in Country R were to add 2 percent of one's annual income to the average of 100 units of County R's currency and 1 percent of one's annual income. Which of the following represents the simplified formula for computing the income tax, in County R's currency, for a person in that country whose annual income is I?答案是：50+I/40
这道题目应该怎么理解啊？标记的那句话我不明白是什么意思，式子要怎么列呢？！
求NN帮助！！

linmeimei

2%I + (100+1%I)/2

mereimoun

这道我前天好像刚刚做过
就是他的税收方法是
百分之2的个人年收入加上100货币值和百分之一年收入的平均值
就是2%I+（100+1%I）/2
=1/50I+50+1/200I
=50+1/40I