Target: state opportunity cost precisely and avoid treating every possible alternative as an additive cost. Prepare: Card B and scarcity ledger.
- Launch · 2 min. Ask what using B's final two hours for digital help prevents in the stated case.
- Model · 4 min. The stated next-best feasible alternative is cataloguing 24 books. So the opportunity cost, expressed in that output, is 24 returned books catalogued. The card does not tell whether digital help is worth more.
- Guided reading · 5 min. Invite a second imagined alternative, such as shelf labels. Explain that it cannot replace the stated next-best alternative without new ranking evidence.
- Practice route · 7 min. Choose Day 2 route; write the decision, feasible alternative, opportunity cost and one value limit for B. Compare D without inventing a numeric cost.
- Audit · 4 min. Partner adds both 24 books and an invented shelf-label count. Learner removes the unsupported addition and names the next-best alternative criterion.
- Exit · 3 min. “Is the 24-book cost the same as a $24 expense?” Key: no, it is the forgone output in this model.