How to arrange the working hours of the 24-hour billiard room?

There are three classes. The 24-hour billiard room can be divided into three time periods, namely, 2 am to noon 12 and 10. There is little traffic at night, so people can have a full rest, so they have arranged long hours of work. 7-hour working hours 12 to 19 are normal working hours. Yes 19 to catch dinner after work. 19: 00 to 2: 00 am the next day, which is 7 hours of working time. At this time, there are many people after dinner, and they need plenty of energy to ensure the state at work.