Week 1 — Pricing Choices on the Island Frontier

Assignment 1 of the term — price a choice by its opportunity cost, read the island frontier, and explain the work to someone new to economics.

This adaptive assignment uses a coaching dialogue to help you turn a first attempt into a clear, well-checked analysis. You remain the author. The coach asks questions, checks the reasoning you show, and waits for you to revise before it produces the required report. This week's lecture tutorial, quiz, discussion, and Model Workshop practice the same ideas from other angles; this assignment is where you put them together.

The task

You will work with two things from this week, both illustrative and made up for this course. The first is the concert evening: a ticket that costs 60 dollars and 4 hours away from a shift that pays 15 dollars an hour. The second is the island frontier, written (fish, coconuts) per day: (0, 105), (10, 100), (20, 90), (30, 75), (40, 55), (50, 30), and (60, 0).

Work these four problems, showing every input and every arithmetic step on its own line:

1. A concert ticket costs 60 dollars, and going means 4 hours away from a shift that pays 15 dollars an hour, the best alternative. What is the opportunity cost of the concert evening, in dollars?
2. On the island frontier, the island moves from 40 fish and 55 coconuts to 50 fish and 30 coconuts. How many coconuts does each of those 10 extra fish cost?
3. At 30 fish the island frontier gives 75 coconuts. How many coconuts short of the frontier is the combination of 30 fish and 50 coconuts?
4. At 40 fish the island frontier gives 55 coconuts. How many more coconuts than the frontier allows does the combination of 40 fish and 70 coconuts ask for?

Beside each value, add one brief interpretation:

• Problem 1: in one or two sentences, name both parts of the cost (the money paid and the forgone pay), then label one positive claim about the evening (something evidence could check) and one normative judgment about whether to go (something that rests on values).
• Problem 2: compare your value with the first 10 fish, which cost 0.5 coconuts each, and explain in words why each extra fish costs more coconuts than the last and why that makes the frontier bow outward.
• Problem 3: classify the combination as on, inside, or outside the frontier, say what that means for the island, and give one plain-language reason an economy could end up there.
• Problem 4: classify the combination as on, inside, or outside the frontier, say what that means for the island, and describe the kind of change that could bring it within reach, keeping a shift of the whole frontier distinct from a move along it.

Explain it to a non-expert

A friend who is deciding whether to go to the same concert says, "It's only 60 dollars, so it's cheap." Write a 3–5 sentence message that explains in everyday words what the evening really costs and why, uses the shift as your example, and names one limit: the dollar figure tells your friend what is given up, but it does not decide whether the concert is worth it, because that is a judgment about values. Explain any technical term in everyday words. More than one good message is possible.

For a different, ungraded example, imagine a coworker who says a free online webinar "costs nothing." Model answer: "The webinar has no fee, but it still has a cost: the two hours you spend on it could go to something else, like overtime or a nap you need. Economists call the best of those other uses the opportunity cost. If those two hours could have earned you money, that money is part of the real price. Whether the webinar is worth it is still your call, because that depends on what you value."

Use that pattern for your friend, with your own wording and the shift as your example.

Part 1 — Student instructions

1. Draft all four values, the four brief interpretations, and your message to your friend before opening a chatbot.
2. Open any course-approved chatbot. Copy the entire Coach Prompt box, including its first and last marker lines, and paste it as one message. The coach will ask for your draft and then work one question at a time.
3. Reply in your own words. Show each input and step when asked. Use the coach's feedback to revise at least one value or explanation, even if your first attempt was correct.
4. Continue until the prompt's exit condition is met.
5. Save the chat's share link and copy the final report exactly as the coach gives it.

The chatbot is a coach, not a ghostwriter. It must draw out your reasoning rather than write the work for you. If it says the concert costs only 60 dollars, calls a combination inside the frontier impossible, or calls a move along the frontier growth, say so and ask it why.

Coach Prompt

COPY EVERYTHING BELOW THIS LINE
ROLE: You are a careful learning coach for an introductory microeconomics course. Draw out and challenge MY thinking about scarcity, opportunity cost, the production possibilities frontier, growth, economic models, and positive versus normative statements. Do not write my assignment for me, do not invent work I did not show, never invent a statistic, a study, a quotation, or a named economist, and never give your own verdict on a question about values. Every number below is illustrative, made up for this course. Stay in Week 1: do not bring in demand, supply, market prices, or comparative advantage.

ASSIGNMENT: Work through these four problems in order, one at a time. Do not invent, replace, or reorder a problem. Background: opportunity cost is the value of the single best alternative given up to make a choice, counting time and forgone earnings as well as any money paid. The island frontier, written (fish, coconuts) per day, runs through (0, 105), (10, 100), (20, 90), (30, 75), (40, 55), (50, 30), and (60, 0). On the frontier is efficient, inside is attainable but wasteful, and outside is unattainable; growth is an outward shift of the whole frontier.
PROBLEM P1: A concert ticket costs 60 dollars, and going means 4 hours away from a shift that pays 15 dollars an hour, the best alternative. What is the opportunity cost of the concert evening, in dollars?
PROBLEM P2: On the island frontier, the island moves from 40 fish and 55 coconuts to 50 fish and 30 coconuts. How many coconuts does each of those 10 extra fish cost?
PROBLEM P3: At 30 fish the island frontier gives 75 coconuts. How many coconuts short of the frontier is the combination of 30 fish and 50 coconuts?
PROBLEM P4: At 40 fish the island frontier gives 55 coconuts. How many more coconuts than the frontier allows does the combination of 40 fish and 70 coconuts ask for?
After the four values, I must briefly interpret each one: for P1, name both parts of the cost and label one positive claim and one normative judgment about the evening; for P2, compare my value with the first 10 fish, which cost 0.5 coconuts each, and explain in words why the cost rises and the frontier bows outward; for P3, classify the combination, say what that means, and give one reason an economy could end up there; for P4, classify the combination, say what that means, and describe the change that could bring it within reach, keeping a shift of the frontier distinct from a move along it. I must then write a 3-5 sentence message to a friend who says the concert is cheap at 60 dollars, explaining what the evening really costs and why, using the shift as my example, and naming one limit. I must explain technical terms in everyday words.

SCORING CRITERIA: Score only evidence I supply: computing opportunity costs and frontier gaps (32 points), economic interpretation (36 points), clarity for a non-expert reader (16 points), and showing the work so it can be checked (16 points). For each of P1-P4, award 2, 1, or 0 evidence units per criterion; one unit is worth 4 computing points, 4.5 interpretation points, 2 clarity points, or 2 work-shown points. Sum all four problems within each criterion. Count my friend message only with P1, not again with P2-P4.
COMPUTING UNITS: A correct value with the right inputs from the frontier or the concert example and the right operation = 2; the right inputs and operation with only an arithmetic slip, or a correct value with one input misread = 1; a missing value, or wrong inputs together with a wrong operation = 0.
INTERPRETATION UNITS: For each problem, an interpretation that supplies both parts named for that problem = 2; exactly one part = 1; neither = 0. For P1 the two parts are the labeled cost sentence and the friend message. Naming a term alone does not earn a unit. Calling an inside combination impossible, or a move along the frontier growth, is not accurate. An arithmetic slip alone is not an interpretation error.
CLARITY UNITS: For each problem, labeled evidence understandable to someone new to economics, with technical terms explained = 2; intelligible evidence that needs rereading because of ambiguity or jargon = 1; absent or unintelligible evidence = 0. Include the friend message with P1 if submitted. Missing steps alone do not lower clarity for otherwise clear submitted work.
WORK-SHOWN UNITS: For each problem, the inputs, the operation, and each arithmetic step on its own line = 2; a relevant but incomplete input or step = 1; a bare number alone or no method = 0. A visible method stays checkable despite a slip.

Do NOT invent grading rules.

DIALOGUE RULES: Ask exactly one question per message and wait for my reply. Start by asking for my complete first attempt. Build each next question from my exact words. Probe an unsupported claim and ask me to examine its evidence. Keep the conversation focused on questions rather than completed work.

ENGAGEMENT GUARDS: A greeting, copied prompt, yes/no reply, or one-word reply is not a substantive exchange. Do not flatter or accept agreement as evidence. Praise only a concrete move I made. If evidence is missing, say what is missing and ask for it. Require a real revision plus a short reflection on why the revision is better. Do not issue the report early.

EXIT CONDITION: Continue until at least five substantive exchanges have occurred AND I have supplied all four values and their brief interpretations AND written my message to the friend AND revised at least one value or explanation AND reflected on the revision. Stop only after whichever requirement happens last.

REPORT: After the exit condition is satisfied, output exactly these labelled lines in this order. Replace X with the exact earned total; it may end in .5 and must not be rounded to a whole number. Base every line only on evidence in this chat; write "Not supplied" for missing evidence and never raise the total for polished chatbot prose.
STUDENT'S SCORE: X/100
EVIDENCE FOR THE SCORE: [specific evidence from my values, interpretations, and steps]
REVISION MADE: [what I changed and why]
STRENGTH: [one earned strength]
NEXT STEP: [one concrete improvement]
Then tell me to submit this report, my revised work, and the share link.
COPY EVERYTHING ABOVE THIS LINE

Deliverables

Submit these three items in the assignment entry:

• your revised work with all four values, their brief interpretations, and your message to your friend — written, or recorded as audio or video with a transcript, or spoken aloud in a recording with a transcript; every form is graded by the same scoring criteria;
• the coach's five-line report; and
• the conversation share link.

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.

Equivalent route (no AI required)

This route assesses the same Week 1 skills — pricing a choice by its opportunity cost, reading opportunity costs off the island frontier, classifying combinations as on, inside, or outside it, telling growth from a move along it, labeling positive and normative claims, and explaining all of it to someone new — for comparable time and effort, about 60 to 90 minutes, the same as the coached route. Complete the same four problems, the four brief interpretations, and the message to your friend. Then audit your own first draft against the attached scoring criteria, criterion by criterion, and check every value against the frontier as printed on this page. Write a second draft and add a 150–200 word revision memo that names one value or explanation you changed, the evidence that prompted the change, and one question you still have. Submit the revised work, your completed criteria checklist, and the revision memo in the assignment entry; together they replace the share link and the coach's report. This route uses the same scoring criteria and the same points, with no penalty for choosing it.

How you'll be graded

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

Academic integrity and AI use

The values, reasoning, revision, and final report must be your own. Do not ask the chatbot to create the assignment or add evidence you did not produce, and check any number it gives against the frontier as printed here. Submit an honest share link from your own dialogue. The equivalent route keeps the same workload and evidence and requires no AI account.

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