What-all the Total average for Rank of 6, when is like smaller as 0?
Rank Nation Gold Silver Bronze Total
Equestrian at the 1980 Summer Olympics
1461487
real text real real real real
2-1461487-1
Medals
Medals
1 Soviet Union (URS) 3 3 2 8
2 Italy (ITA) 1 1 0 2
2 Poland (POL) 1 1 0 2
4 Austria (AUT) 1 0 0 1
5 Bulgaria (BUL) 0 1 0 1
6 Mexico (MEX) 0 0 3 3
7 Romania (ROU) 0 0 1 1
SELECT AVG Total FROM table WHERE Rank = 6 AND Silver < 0
6 0