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Explain a mid-cycle upgrade charge with the proration math

  • For Customer support teams
  • You practice Catching mistakes and made-up facts
  • Time about 5 minutes
  • Level Intermediate

About this exercise

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.

Common mistakes when you ask AI for this

  • Using the old difference rule. The AI says $60 minus $30 = $30. Try: Say: "Use days remaining / 30 for both plans."
  • Math described not shown. The AI says 'we prorated' without numbers. Try: Say: "Show each calculation on its own line."
  • Wrong open or close. The AI writes its own greeting and sign-off. Try: Give the exact greeting and sign-off.
  • Getting markdown back. AI adds bold and headings by default, which show up as stray symbols where this is pasted. Try: Say "plain text, no bold, no headings, no asterisks".
  • Trusting the AI to count words. AI is bad at counting and usually runs long, so a vague "keep it short" lands well over the limit. Try: Cap each part instead of the total, for example "each line under 15 words".

What a strong prompt includes

  • Asks to show the three calculations
  • Gives the exact greeting and sign-off
  • Mentions the renewal
  • Asks for plain text
  • Sets a length limit

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