Question 28
$A$, $B$ and $C$ are three persons among a set $P$ of $n$ ($n \ge 3$) persons. It is known that $A$, $B$ and $C$ are friends of one another, and that every one of the three persons has already made friends with more than half the total number of people in $P$. Given that every three persons who are friends of one another form a *friendly group*, what is the minimum number of friendly groups that may exist in $P$?