{"id":"cx-upgrade-proration-email-math","audience":"customer-support","category":"support-work","technique":"verification","track":"support","level":"intermediate","title":"Explain a mid-cycle upgrade charge with the proration math","free":false,"task":"Write an email to Kofi that shows the three calculations on their own lines (credit for the unused Basic days, cost of Pro for the remaining days, and the charge today), then a sentence about his next renewal. Open with \"Hi Kofi,\" and end with \"Rae, Billing Help\". Plain text, under 110 words.","materialLabel":"Your material (attached to your prompt automatically)","material":"CUSTOMER QUESTION\nKofi Mensah upgraded from Basic to Pro today (Nov 11) and asks 'Why was I charged $20 and not $60? I thought Pro was $60.'\n\nBILLING FACTS\n- Basic: $30 per month. Pro: $60 per month.\n- Billing cycle: Nov 1 to Nov 30 (30 days). Renews on Dec 1.\n- Kofi used Basic for 10 days (Nov 1 to Nov 10). 20 days remain in the cycle.\n- On an upgrade we credit the unused part of the old plan and charge the remaining days of the new plan: price x days remaining / 30.\n- The charge today is the new-plan cost minus the credit.\n- From Dec 1 he pays the full $60 each month.\n\nOLD NOTE (ignore): 'Upgrades are charged the difference in price' (this was the 2022 rule).","rules":[{"type":"plainText"},{"type":"maxWords","max":110}],"mistakes":[{"title":"Using the old difference rule","why":"The AI says $60 minus $30 = $30.","fix":"Say: \"Use days remaining / 30 for both plans.\"","checks":["r1","r2"]},{"title":"Math described not shown","why":"The AI says 'we prorated' without numbers.","fix":"Say: \"Show each calculation on its own line.\"","checks":["r1"]},{"title":"Wrong open or close","why":"The AI writes its own greeting and sign-off.","fix":"Give the exact greeting and sign-off.","checks":["r0"]},{"title":"Getting markdown back","why":"AI adds bold and headings by default, which show up as stray symbols where this is pasted.","fix":"Say \"plain text, no bold, no headings, no asterisks\".","checks":["plainText"]},{"title":"Trusting the AI to count words","why":"AI is bad at counting and usually runs long, so a vague \"keep it short\" lands well over the limit.","fix":"Cap each part instead of the total, for example \"each line under 15 words\".","checks":["maxWords"]}],"promptHints":[{"label":"Asks to show the three calculations","patterns":["three (calculations|lines)","show the (math|calculation)"]},{"label":"Gives the exact greeting and sign-off","patterns":["hi kofi","rae, billing help"]},{"label":"Mentions the renewal","patterns":["dec 1","renew"]},{"label":"Asks for plain text","patterns":["plain","no bold","no markdown","no formatting","no headings"]},{"label":"Sets a length limit","patterns":["\\d+\\s*words","word (limit|count)","under \\d+"]}],"hint":"Ask for each calculation on its own line, with the formula, and give the exact open and close.","rubricLabels":["The email starts with \"Hi Kofi,\" and ends with the line \"Rae, Billing Help\"","Three lines show the math: Basic credit $30 x 20/30 = $20, Pro cost $60 x 20/30 = $40, and today's charge $40 - $20 = $20","A sentence says he pays the full $60 from Dec 1 and the email does not say the upgrade is charged as a $30 difference"]}