### Chinese: 等你真的能分辨好坏，说明你进步了，到时候再来我这里买贵的，我赚两次钱。
### English: When you can distinguish good ones from poor ones, you get progress; you will but expensive ones again, and I can sell two times of tennis rackets by earning two times of money.
### Errors: There is no error in the English translation.

### Improved English: If you can tell the difference, it means you have made improvement; then you can come here to buy the expensive ones and I will make money twice.
