Jim’s utility function is U(x, y) = xy. Jerry’s utility function is U(x, y) = 1, 000xy + 2, 000. Tammy’s utility function is U(x, y) = xy(1 − xy). Oral’s utility function is U(x, y) = −1/(10+ 2xy). Marjoe’s utility function is U(x, y) = x(y + 1, 000). Pat’s utility function is U(x, y) = 0.5xy − 10, 000. Billy’s utility function is U(x, y) = x/y. Francis’ utility function is U(x, y) = −xy.

a) Who has the same preferences as Jim?

b) Who has the same indifference curves as Jim?

c) Explain why the answers to (a) and (b) differ.