Each pair of circles intersect twice
So.....we have a set of n circles and we want to choose any two of them = C (n, 2)
And since each pair intersects twice, the number of intersection points = 2 C(n , 2) =
2 n! / [ (n - 2)! * 2! ] = n! / ( n - 2)! = n ( n - 1)
So.....The max intersection points of n circles = n(n - 1)
So..... 4(4 - 1) = 4 (3) = 12
Just as EP found !!!!