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June buys both ham (x) and cheese (y) for her sandwiches. Her preferences over t

ID: 1169599 • Letter: J

Question

June buys both ham (x) and cheese (y) for her sandwiches. Her preferences over these two goods can be represented by the utility function u(x, y) = min{x, 2y}. That is, ham and cheese are perfect complements. Suppose June has income I = 60 to spend on ham and cheese. The price of a slice of ham is px = 2 and price of a slice of cheese is py = 1. Use the utility function given above to find her best consumption bundle (x*,y*). Suppose now that the price of a slice of ham is px = 1 and price of a slice of cheese is py = 2. Find the new optimal consumption bundle (x*,y*). Comparing your result in part (a) and (b), does it imply an upward sloping demand curve for cheese (y)?

Explanation / Answer

u = min [x, 2y]

This utility function signifies that x and y are perfect complements (L-shaped indifference curves].

(a) Budget line: I = xpx + ypy

60 = 2x + y

For perfect complements, optimal consumption bundle is when x = 2y

Substituting in budget line,

60 = 2 x 2y + y = 5y

y = 12

x = 2y = 24

(x*, y*) = (24, 12)

(b)

Revised budget line:

60 = x + 2y

Optimum bundle stays the same at x = 2y.

60 = 2y + 2y = 4y

y = 15

x = 2y = 30

(x*, y*) = (30, 15)

(c)

When py = 1, y = 12

When py = 2, y = 15

As price increases, quantity of y increases. This suggests an upward sloping demand curve.