Mk 408

---
name: mk-408
description: "Cost per Friend Calculation. Use when work requires a consistent basis for spending and valid newly added friends; process the specified inputs using this method and verify the deliverable"
---

# MK-408 | Cost per Friend Calculation

For ordinary chat, upload `packs/mk-408.md`, which includes the shared rules, this method, and required references

## Purpose

This skill delivers: **A consistent basis for spending and valid newly added friends**

Do not send messages or create automation without approval; if a tool cannot show recipient eligibility, do not assume everyone can be messaged

## Required inputs

Provide: friend or subscriber status, permissions, product content, campaigns, and channel reports

## Method steps

1. CPF = LAP advertising spend ÷ newly added friends
2. CPF is only the entry cost of obtaining permission for continued communication, rather than the final outcome
3. Use advertising spend and newly added friends from the same period; do not force a cost calculation when there are zero new friends

## Calculation and interpretation

Verify contact consent, unsubscribes, and message specifications; friend counts and open rates are not sales

## Required output fields

| Order | Field | How to fill it in |
|---:|---|---|
| 1 | Variable | Original evidence, intermediate method results, or an explicit unknown; do not fabricate |
| 2 | Definition | Original evidence, intermediate method results, or an explicit unknown; do not fabricate |
| 3 | Source / unit | Original evidence, intermediate method results, or an explicit unknown; do not fabricate |
| 4 | Formula | Original evidence, intermediate method results, or an explicit unknown; do not fabricate |
| 5 | Input value | Original evidence, intermediate method results, or an explicit unknown; do not fabricate |
| 6 | Result | Original evidence, intermediate method results, or an explicit unknown; do not fabricate |
| 7 | Missing items / limitations | Original evidence, intermediate method results, or an explicit unknown; do not fabricate |

## Verification cases

**MK-408-A1 | Same-period LAP spend100 and ten new friends**

Expected: CPF = 10, retaining acquisition definition/window

**MK-408-A2 | Zero new friends**

Expected: CPF undefined, not zero cost

## Method sources

Original file: 行銷策略實戰學程 Day5｜Google Ads × LINE｜線上課程用投影片

Source locator: LINE

Source basis: extracted from course materials

Original URL: https://docs.google.com/presentation/d/1RK8wiunlvJrRxgFuTcGhO5B5fRa4fbEogpZTJpF6YKc/edit

English translation of source excerpt retained in the master sheet:

> Google Ads × LINE