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Report CAC and payback under two definitions without choosing

  • For FP&A and financial analysts
  • You practice Keeping the AI to your sources
  • Time about 5 minutes
  • Level Advanced

About this exercise

You're giving the CFO CAC and payback under the two definitions in use. Write a prompt for plain text with lines starting "Marketing CAC:", "Fully loaded CAC:", "Payback (marketing):", "Payback (fully loaded):" and "Not decided:". Marketing CAC uses marketing program spend only; fully loaded CAC adds the attributable sales cost. Payback months = CAC divided by monthly gross margin per customer, one decimal. Show the math. Do not say which definition to report. Under 110 words.

Common mistakes when you ask AI for this

  • Blending the two. The AI reports one CAC. Try: Say: "Give both definitions on separate lines."
  • Picking a definition. The AI recommends fully loaded. Try: Add: "Do not say which definition to report."
  • Skipping the payback math. The AI states payback without dividing. Try: Add: "Show CAC / monthly margin for each."
  • Markdown extras. The AI adds bold labels, headings and a closing note. Try: Say: "Plain text, no bold. Output only the lines asked for."
  • Trusting the AI to count words. AI is bad at counting and runs past word limits. Try: Ask for fewer words than the real cap and keep each part short.

What a strong prompt includes

  • Names the five lines
  • Defines both CACs
  • Gives the payback formula
  • Bans picking
  • Caps length

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