{"id":"fpa-capex-payback-lines","audience":"fpa","category":"finance-work","track":"finance","technique":"constraints","level":"intermediate","title":"Compute simple paybacks and spot the one that never pays back","free":false,"task":"You're comparing three capital requests for the CFO. Write a prompt for plain text with lines starting \"Project A:\", \"Project B:\", \"Project C:\" and \"Fastest payback:\". Each project line shows cost / monthly savings = months, or says \"No payback within the savings period\" with the math. Facts only: no recommendation to approve or reject. Under 80 words.","materialLabel":"Three capital requests (attached to your prompt automatically)","material":"CAPITAL REQUESTS - Q1 2027 planning, Ridgeway Distribution\n\nProject A: Warehouse barcode scanners. Cost $60,000. Expected labor savings $2,500 per month, starting the month after go-live.\n\nProject B: Replace the legacy shipping software. Cost $18,000. It would save $900 per month in license fees, but the legacy license it replaces ends after 12 months and the savings stop at that point.\n\nProject C: Dock HVAC upgrade. Cost $120,000. Expected energy savings $3,000 per month.\n\nFinance notes: Simple payback = cost / monthly savings. Ignore financing, taxes and discounting. All three requests are signed off by the sponsor.\nOps director wrote: \"B is obviously the cheapest so it should go first.\"","rules":[{"type":"plainText"},{"type":"maxWords","max":80}],"promptHints":[{"label":"Names the four lines","patterns":["project a:","fastest payback"]},{"label":"Gives the formula","patterns":["cost / monthly savings","payback"]},{"label":"Handles ending savings","patterns":["stop","no payback","total savings"]},{"label":"Bans recommendations","patterns":["(do not|don'?t).*(recommend|approve)"]},{"label":"Caps length","patterns":["\\d+\\s*words","plain"]}],"mistakes":[{"title":"Computing B as 20 months","why":"The AI divides $18,000 by $900 and ignores that savings stop at 12 months.","fix":"Add: \"If savings stop before cost is recovered, say no payback and show total savings vs cost.\"","checks":["r1"]},{"title":"Echoing the ops director","why":"The AI picks B because it is cheapest.","fix":"Add: \"Ignore opinions in the notes. Fastest payback = fewest months.\"","checks":["r2"]},{"title":"Missing arithmetic","why":"The AI gives months without cost / savings.","fix":"Say: \"Show cost / monthly savings = months.\"","checks":["r0"]},{"title":"Markdown extras","why":"The AI adds bold labels, headings and a closing note.","fix":"Say: \"Plain text, no bold. Output only the lines asked for.\"","checks":["plainText"]},{"title":"Trusting the AI to count words","why":"AI is bad at counting and runs past word limits.","fix":"Ask for fewer words than the real cap and keep each line short.","checks":["maxWords"]}],"hint":"One request has savings that stop early. Give the formula and the no-payback wording, and ban recommendations.","rubricLabels":["Project A line shows $60,000 / $2,500 = 24 months and Project C line shows $120,000 / $3,000 = 40 months","Project B line says no payback within the savings period because $900 x 12 = $10,800 is less than $18,000","Fastest payback line names Project A (24 months) and nothing recommends approving or rejecting a project"]}