LEBLOCKS test case explain?

Can somebody be kind enough to explain test case of LEBLOCKS
http://www.codechef.com/JUNE14/problems/LEBLOCKS \

Input:
1
7 5
3 1
2 2
2 1
4 3
1 2
1 3
4 4

Output:
0.9095238

try to write a brute force code…yu will get the ans.

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