Each chart has an x-axis labeled “Smoothies (per hour)” from 0 to 30 in increments of 5 and a y-axis labeled “Salads (per hour)” from 0 to 30 in increments of 5.

In graph (a), which is titled “Liz’s gain from trade”, a line labeled “Liz’s PPF” passes through (0, 30), (15, 15), and (30, 0). The point A(15, 15) is labeled “1”, the point B(30, 0) is labeled "2", and a point C(20, 20) that is above the line is labeled "3". The point B is labeled "Liz produces here" and the point C is labeled "Liz buys 20 salads from Joe"

In graph (b), which is titled “Joe’s gain from trade”, a line labeled “Joe’s PPF” passes through (0, 30), (5, 5), and (6, 0). The point A(5, 5) is labeled “1", the point B(0, 30) is labeled "2", and the point C(10, 10) is labeled "3". ...

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