In the graph, how much of Y must be given up to move from point M to 30 units of X along the PPC?

Explanation

1. 01

   At M the economy makes 20 X and 10 Y; the MRT is 0.5 Y per X.

2. 02

   Ten more units of X cost 10 × 0.5 = 5 units of Y, leaving 5 Y.