Suppose the United States is initially an autarky. Figure 17P-3 shows the domestic market for paper. When the U.S. does not allow trade, the world price is $0.30. When the United States does allow trade, the world price falls to $0.20.

Based on the figure, which of the following statements is correct? 

a. The increase in world demand for paper was larger than the increase in world supply of paper. 

b. The decrease in world demand for paper was larger than the increase in world supply of paper. 

c. The increase in world supply of paper was larger than the increase in world demand for paper. 

d. The decrease in world supply of paper was larger than the increase in world demand for paper.