Suppose the nation of Arcadia produces only two goods, teapots and surfboards. If Arcadia produces teapots, it can make 40 per day. If Arcadia produces only surfboards, it can make 60 per day. What is the opportunity cost of one teapot in Arcadia?
a. 2/3 of a surfboard
b. 1.5 surfboards
c. 40 surfboards
d. 60 surfboards