The Following Graph Shows the Supply of and Demand for Baseballs

The following graph shows the supply of and demand for baseballs in the United States. If the world price is $3 per baseball and a tariff of $1 per baseball is imposed, then the number of baseballs purchased in the United States is _____. ​
Figure 19.3
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A) 4,000
B) 6,000
C) 8,000
D) 10,000
E) 12,000