Need help in understanding question

#1

pl explain the queation ,also test case not clear to me

#2

@spagire4
In this problem, you are given n clues in the form of n strings.
You have to find a code with the help of the given clues based on the length of longest common prefix of (ai, aj).
It will too large to dry run this approach the example you have given.

Solution:
This is question of Trie.
what we do is for all nodes of the trie , we calculate number of strings in the substree and then just apply combinatorics.