Week 2 — Who Should Make the Sandwiches? A Short Trade Report — Traditional alternative (no AI)

Instructors: publish this instead of the adaptive version if you prefer, and unpublish or delete the adaptive one.

Assignment 2 of the term — work out who should make what at an illustrative food stand, prove that both partners gain from trading, and explain the result to someone new to economics.

This assignment asks you to work a short trade report on your own and then check and revise it yourself. Last week you learned that every choice has an opportunity cost; this week that idea decides who should make what. This week's lecture tutorial, quiz, discussion, and Model Workshop practise the same ideas from other angles; this assignment is where you put them together on one question: who should make the sandwiches, and does anyone lose?

The task

You will use Dataset D, the campus food stand, an illustrative dataset constructed for this course (not real data). In one hour, Amara can make 8 smoothies or 4 sandwiches, and Diego can make 3 smoothies or 3 sandwiches. Each partner works 8 hours. Before trade, each splits the hours evenly, so Amara makes 32 smoothies and 16 sandwiches and Diego makes 12 smoothies and 12 sandwiches. Then Diego makes only sandwiches (24), Amara spends 6 hours on smoothies and 2 on sandwiches (48 smoothies and 8 sandwiches), and they trade at 1.5 smoothies per sandwich.

Work these four problems, showing your arithmetic and writing the units on every ratio:

1. At the illustrative campus food stand, Amara can make 8 smoothies or 4 sandwiches in one hour. What is her opportunity cost of making one sandwich, in smoothies per sandwich?
2. At the illustrative campus food stand, Amara can make 8 smoothies or 4 sandwiches in one hour. What is her opportunity cost of making one smoothie, in sandwiches per smoothie?
3. At the illustrative campus food stand, Diego trades 10 sandwiches to Amara at 1.5 smoothies per sandwich. How many smoothies does Diego receive?
4. At the illustrative campus food stand, Amara makes 16 sandwiches before trade; after specializing she makes 8 sandwiches and then receives 10 from Diego. How many more sandwiches does Amara have after the trade than before trade?

Beside each result, add one brief interpretation. For P1, say what the cost means and compare it with Diego's cost of 1 smoothie per sandwich to name who has the comparative advantage in sandwiches; keep that apart from who is faster. For P2, say how this cost relates to the P1 cost and compare it with Diego's cost of 1 sandwich per smoothie to name who has the comparative advantage in smoothies. For P3, check whether 1.5 lies between the two opportunity costs of a sandwich, and say why each partner accepts the rate. For P4, use the stand's totals, 44 smoothies and 28 sandwiches before trade and 48 and 32 after specializing, to explain how both partners can gain at once.

Explain it to a non-expert

A friend who runs a two-person bike-repair shop says, "I'm faster than my partner at both repairs and sales, so I should do everything myself." Write a 3–5 sentence message that answers your friend using what your results show, gives a reason tied to the food-stand data, and names one limit of the model — for example, that the numbers are illustrative, or that the model assumes each person's cost stays the same hour after hour. Explain any technical term, such as opportunity cost or comparative advantage, in everyday words. More than one way of putting it can be correct.

For a different, ungraded example, imagine two siblings splitting yard work, where the older one mows and rakes faster than the younger one. Model answer: "Being faster at both jobs doesn't mean you should do both. Every hour you spend raking is an hour of mowing you give up, and your sibling gives up less mowing for each bag raked. If you mow and your sibling rakes, the yard gets done sooner. This assumes neither of you gets tired, which real afternoons don't promise."

Use that pattern for the bike-repair shop, with your own results and reasoning.

Check and revise your own draft

When your first draft is complete, check it against the attached scoring criteria, criterion by criterion. Make sure every ratio carries its units, that you named comparative advantage by the lower cost rather than by speed, and that each interpretation says what the number means. Revise at least one calculation or explanation, and add a 100–150 word revision note that names what you changed and why the new version is better. Choose one of two reflection questions for the last two sentences of that note: (a) which of this week's slips, an inverted ratio or giving the comparative advantage to the faster partner, you came closest to making, and how you caught it; or (b) where in your own life you divide tasks with someone, and who has the lower opportunity cost for each.

Deliverables

Submit these two items in the assignment entry:

• your revised trade report with all four results, their brief interpretations, and your message to the bike-shop friend — written, or recorded as audio or video with a transcript, or as a labelled spreadsheet with a short note; every form is graded by the same scoring criteria; and
• your revision note with its reflection.

Submit in any accessible file type or as a link; a recorded response may be submitted as audio or video with a transcript, or as text.

How you'll be graded

The full analytic rubric is attached to this assignment in Canvas.

Academic integrity and AI use

The calculations, reasoning, revision, and final report must be your own work. This version of the assignment is designed to be completed without any AI tool; use the chapter, the lecture, and your notes. Cite any source you consult beyond the course materials.

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