GMAT
题目
Each writer for the local newspaper is paid as follows: a dollars for each of the first n stories each month, and a + b dollars for each story thereafter, where a > b. How many more dollars will a writer who submits n + a stories in a month earn than a writer who submits n + b stories?
解析
一个月提交\( n + a \)篇稿件的作者的收入：
\( a*n + (a+b)*a \)
一个月提交\( n + b \)篇稿件的作者的收入：
\( a*n + (a+b)*b \)
两人的收入差 = \( [a*n + (a+b)*a] - [a*n + (a+b)*b] = (a+b)(a - b) = a^2 - b^2 \)
答案：选项C
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