Five distinct families arrive to a party. Each family consists of 3 people. The 15 participants of the party are arranged randomly in a line. 

Let X be the number of families that their members sit next to each other. Find E[X] and Var(x).

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My attempt: Just go straight to find out the pmf of X, P(X=1), P(X=2)... up to P(x=5). Does this question ask for all members of at least 2 of the family members? If it is the second case, I have no idea how to do it.