3.13 Professor Goodheart's colleague Dr. Kremepu gives 3 midterm exams. He drops the lowest and gives each student her average score on the other two exams. Polly Sigh is taking his course and has a 60 on her first exam. Let x2 be her score on the second exam and x3 be her score on the third exam. If we draw her indifference curves for scores on the second and third exams with x2 represented by the horizontal axis and x3 represented by the vertical axis, then her indifference curve through the point (x2; x3) = (50; 70) is:

(a) L-shaped with a kink where x2 = x3.

(b) three line segments, one vertical, one horizontal, and one running from (70; 60) to (60; 70).

(c) a straight line, running from (0; 120) to (120; 0).

(d) three line segments, one vertical, one horizontal, and one running from (70; 50) to (50; 70).

(e) a V-shaped curve with its point at (50; 70).