the weekly free time

every week, i have free time on thursday. because, the schedule time, that the department leader board give me, is very illogical. in this schedule time, i teach only 4 hours in the affternoon, but they arrange me 2 hours for one subject first and then 2 hours free time, and 2 hours left for one subject. this means that i have 2 hours for something not relating to teaching such as coffee, chatting and etc.