max books that can be borrowed by 30 students is 30 * 2 =60
Now 2 students dont borrow any book,
remaining student = 28
remaining books = 60
12 students each borrow 1 book,
remaining student = 16
remaining books = 48
10 students each borrow 2 book,
remaining student = 6
remaining books = 28
now 28 books to be borrowed among 6 students.
These students can't borrow 1 or 2 books.... This is the key...
So lets Assume 15 books by a student
remaining student = 5
remaining books = 13
not possible, as someone have to borrow 2 books then...
So next highest 13 books borrowed by a student
again...
remaining student = 5
remaining books = 15
this will do, So 13 books
Ans D
