In a survey of 100 students, it was found that 50 used the College library books, 40 had their own books, and 30 used borrowed books, 20 used both College library and their own books, 15 used their own books and borrowed books, whereas 10 used College library books and borrowed books. Assuming that each student uses either College library books or their own or borrowed books, find the number of students using books from all three sources.