The economy was at point A producing 100X and 200Y. It moved to point B where it produces 200X and 300Y. It follows that: a. point A may have been a point below the economy's PPF, while point B may lie on the PPF.
b. the economy's PPF could have shifted outward and point A was a point on the economy's old PPF.
c. the economy has moved from one point on its PPF to another point on the same PPF.
d. a or b a or c