Firstly , I would straight away go to the class teacher and tell him / her whole matter . Then , I will talk to my friend and make him understand to care about the things which are given to you and also which belongs to other peoples and also I will tell him to go and  say sorry to the teacher and as well as the Library teacher. 
If Library  teacher asks him to pay the money then he should pay the money so that he would remember the incident and don't be careless.
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