https://books.google.com.tr/books?id...0chord&f=false
The question is in the link. There is also the solution.

What I don't understand is the solution.It says : "An edge is counted more than once when it is a common chord of at least 2 circles. Since two circles can have at most one common cord and there are n such circles, the number of common chords, counted with repetition, is at most C(n,2)".

How does he get C(n,2)?

2 circles intersect at 2 points and if we join the 2 points with a line the line is a chord.How does he count the chords?