Consider a change in the table in Problem 2-4. The student's set of opportunities is now as follows:
Economics Biology
100.........................40
90..........................60
80..........................75
70..........................85
60..........................93
50..........................98
40.........................100
Does the PPC illustrate the law of increasing additional cost? What is the opportunity cost to this student for the additional amount of study time on economics required to move her grade from 60 to 70? From 90 to 100?