Every week, Bob plays the piano for one hour and his grade on each psych test is
80 percent. Last week, after playing for one hour, Bob considered playing for another hour. He decided to play for another hour and cut his study time by one hour. But last week, his psych grade fell to 75 percent. Did Bob make his decision on the margin?
A.
Bob’s decision was not made at the margin because he didn't compare the total benefit and total cost of a first hour of playing the piano.
B.
Bob made his decision at the margin because he considered the benefit and cost of one additional hour of playing the piano.
C.
Bob's decision was not made at the margin because the marginal cost of a lower grade always exceeds its marginal benefit.
D.
Bob's decision was not made at the margin because he could have chosen not to play the piano but didn't.
E.
Bob's decision was made at the margin because his grade fell by only 5 percentage points.
