Three pipes A, B, C can fill a tank from empty to full in 30 minutes, 20 minutes, and 10 minutes respectively. When the tank is empty, all three pipes are opened. A, B & C discharge chemical solution 'Q', 'R', 'S' respectively. What is the proportion of solution 'S' in the liquid in the tank after 3 minutes:
1
7/11
2
5/11
3
6/11
4
None of these