Figure 1.13 shows Mendork's production possibility curve for the only two goods that it produces-guns and butter. FIGURE 1.13 a 1b Quantity of Butter (tonnes) N 8 12 16 20 24 28 Quantity of Guns Refer to Figure 1.13 to answer this question. What is the opportunity cost of one more tonne of butter as output changes from point b to a? Select one: O A. 4 guns. O B. 6 guns. C. 10 guns. D. 2 guns. Clear my choice