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Remember our friend Ralph Rigid from Chapter 3? His favorite diner, Food for Thought, has adopted the following policy to reduce the crowds at lunch time: if you show up for lunch t hours before or after 12 noon, you get to deduct t dollars from your bill. (This holds for any fraction of an hour as well.)

(a) Use blue ink to show Ralph's budget set. On this graph, the horizontal axis measures the time of day that he eats lunch, and the vertical axis measures the amount of money that he will have to spend on things other than lunch. Assume that he has 20 total to spend and that lunch at noon costs 10. (Hint: How much money would he have left if he ate at noon? at 1 P.M.? at 11 A.M.?)

(b) Recall that Ralph's preferred lunch time is 12 noon, but that he is willing to eat at another time if the food is sufficiently cheap. Draw some red indifference curves for Ralph that would be consistent with his choosing to eat at 11 A.M.

The answer is given as enter image description here

My question is, shouldnt the graph be perfectly parabolic? with both tangents at Time = 11 and 1. Shouldn't eating at 11 be exactly as preferable to eating at 1?

Thanks for the help.

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I think the answer to your question is that it would be a matter of Ralph's preferences. Perhaps he is indifferent to eating at 11:00 am or 1:00 pm, as you suggest. But he might have non-parabolic preferences (for reasons unspecified), and both this situation and the one you describe are consistent with his eating at 11:00 am, so the answer provided is a correct solution to the question asked. Perhaps the particular indifference curves drawn are a way to avoid multiple solutions (the author might have thought it simpler).

I'm going exclusively off the information in your post though, so I'm assuming that we do not know if Ralph has any preferences over time independent of how it implicitly affects the price he pays.

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There is no reason why Ralph's indifference curves should be parabolic or symmetrical about 12 noon. Their shape will depend on his preferences and circumstances (or, more precisely, on his preferences which will be influenced by his circumstances and may therefore change from one day to another).

Suppose for example that it's a working day and his boss has asked him to attend a meeting at 1 pm. In that case his indifference curves on that day would probably become almost vertical at some time before 1 pm.

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