Why is the answer c

Use the figure below to answer question 7: The figure shows the production possibilities curve for a country that produces two goods, hammers and wrenches. Hammers (thousands) 35 A 29 23 B D 10 C E 0 22 30 4045 Wrenches (thousands) 7. Refer to the figure above. If the economy is currently producing at point B, what is the opportunity cost of moving to point C (producing 10,000 more wrenches)? A. 10 thousand wrenches. B. 10 thousand hammers. C. 13 thousand hammers. D. 40 thousand wrenches