It takes 2 minutes for Party A to fetch water, 2 minutes for Party B, 2 minutes for Party C and 6 minutes for Party D;
It takes 3 minutes for B to fetch water, 3 minutes for C and D, and 6 minutes for * * *;
C takes 4 minutes to get water, and D waits 4 minutes.
6+6+4= 16
Arranging them to take water in the order of A, B, C and D can minimize the total queuing time, which needs at least 16 minutes.