Consider a simple economy producing two goods: cars and milk. The following table gives several points on this economy's Production Possibility Frontier (PPF):

Cars (1000's/year) Milk (1000's of gallons/ year)

0 60

1 50

2 30

3 0

a. Graph this economy's PPF and label the axes as you deem fit; the interpretation of opportunity cost does NOT change with the delineation of the axes.

b. Why is the production possibility frontier downward sloping? Explain the underlying economic logic.

c. Why is the production possibility frontier strictly concave in this case? Note that in some cases the PPF can be 'weakly concave', where a portion of the curve may be a linear segment. Strict concavity rules out such 'weakly concave' segments. Does a linear PPF meet the criterion of both weak concavity and weak convexity?