Which point represents the optimal mix of producing butter and shoes? [Image description: The graph below shows the production possibilities frontier for pairs of shoes and sticks of butter. Vertical axis is pairs of shoes and horizontal axis is sticks of butter. The points on the PPF are as follows: 95 pairs of shoes, 0 sticks of butter; 90 pairs of shoes, 25 sticks of butter (Point C); 85 pairs of shoes, 50 sticks of butter; 70 pairs of shoes, 70 sticks of butter; 50 pairs of shoes, 82 sticks of butter (Point D); 25 pairs of shoes, 90 sticks of butter; and 0 pairs of shoes, 95 sticks of butter. Point A lies within the PPF, at approximately 25 pairs of shoes and 25 sticks of butter. Point B lies outside of the PPF, at approximately 92 pairs of shoes and 92 sticks of butter.]