请教一道关于income tax的Prep DS题

题目是

Before being simplified, the instructions for computing income tax in Country R were to add 2 percent of one's annual income to the average (arithmetic mean) of 100 units of Country R's currency and 1 percent of one's annual income
Which of the following reprentes the simplified formula for computing the income tax, in Country R's currency, for a person in that Country whose annual income is I?

答案是 50+ I/40

关键是我不太理解 to add 2 percent of one's annual income to the average (arithmetic mean) of 100 units of Country R's currency 的意思，请NN帮忙，谢谢！

这个比较难理解,遇到这种情况看到名词就想定义就好,不用怕

to add……to……就是+,所以写2%AI+

average of就是【（）＋（）】/2      所以是100＋1％AI

所以就是2%AI+100＋1％AI

谢谢！这下看懂了