题目内容：

假定英语课上老师要求同桌之间交换修改作文，请你修改你同桌写的以下作文。文中共有10处语言错误，每句中最多有两处。每处错误仅涉及一个单词的增加、删除或修改。

增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。

删除：把多余的词用斜线（\）划掉。

修改：在错的词下划一横线，并在该词下面写上修改后的词。

注意：1. 每处错误及其修改仅限一词；

2. 只允许修改10处，多者（从第11处起）不计分。

Last Friday I took the subway home as usually. Since our physics teacher had just teach us in class that the escalator（自动扶梯） worked, I decided to see how fast the escalator went. To my surprise, it went a speed of about 40 m/min. The next day, I went to a department store with her cousin Emily. I times the escalator here too. I found that it was much slower, going about 30 meter every minute. Why? I check on the Internet and found the reason. Stores slow down escalators on a purpose, allowing customers more time to looking at their products.