what is the number of bronze for the united states?
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col : rank | nation | gold | silver | bronze | total row 1 : 1. | brazil | 21 | 9 | 12 | 42 row 2 : 2. | united states | 9 | 3 | 6 | 18 row 3 : 3. | china | 1 | 9 | 8 | 18 row 4 : 4. | australia | 1 | 1 | 1 | 3 row 5 : 4. | netherlands | 1 | 1 | 1 | 3 row 6 : 6. | estonia | 1 | 0 | 0 | 1 row 7 : 7. | germany | 0 | 5 | 1 | 6 row 8 : 8. | russia | 0 | 2 | 3 | 5 row 9 : 9. | argentina | 0 | 2 | 0 | 2 row 10 : 10. | switzerland | 0 | 1 | 1 | 2 row 11 : 11. | norway | 0 | 1 | 0 | 1 row 12 : 12. | austria | 0 | 0 | 1 | 1
what is the number of bronze for the united states?
Rank Nation Gold Silver Bronze Total
1. Brazil 21 9 12 42
2. United States 9 3 6 18
3. China 1 9 8 18
4. Australia 1 1 1 3
4. Netherlands 1 1 1 3
6. Estonia 1 0 0 1
7. Germany 0 5 1 6
8. Russia 0 2 3 5
9. Argentina 0 2 0 2
10. Switzerland 0 1 1 2
11. Norway 0 1 0 1
12. Austria 0 0 1 1
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