I got this question in a competitive exam i wrote today...n i was just curious if my answer was right.

The Question is :

Let G be a complete undirected graph on 6 vertices. If vertices of G are labelled, then the number of distinct cycles of length 4 in G is equal to

a) 15 b) 30 c) 90 d) 360

I got the answer as 90...am i right??