I am a mechanic. I can answer you that the driver's salary is high, but he is tired. He watches four or five hours in advance, and the mechanic's salary is slightly lower, but he can take a leisurely nap. The mechanic on board is not dirty, but the mechanic on the ground is dirty. The so-called on-board mechanic is to follow the EMU you are responsible for to ensure the safe operation of the EMU you are responsible for. The ground mechanic is the maintenance and repair of EMU after warehousing. It's up to you. If you want to know, you can ask me,