Work(s) in an hourly interval max days per week

[Liviu Lalescu]

By the way, what is meant by " a teacher works in an hourly interval max days per week" ?

It means that in this interval (say from 12:00 to End of day, or any interval), the number of days the teacher works is limited to say 3 days per week. You can decide that in the last 2 hours of each day, each teacher can work at most 2 times a week. It is a nice constraint.