AIME
2010
Define an ordered triple (A,B,C) of sets to be minimally intersecting if |A∩B|=|B∩C|=|C∩A|=1 and A∩B∩C=∅. For example, ({1,2},{2,3},{1,3,4}) is a minimally intersecting triple. Let N be the number of minimally intersecting ordered triples of sets for which each set is a subset of {1,2,3,4,5,6,7}. Find the remainder when N is divided by 1000.
Note: |S| represents the number of elements in the set S.