ORIGINAL WORKED REFERENCE

At price 25, contribution is 15 and break-even is 900 / 15 = 60 copies. At 80 copies, surplus is 300. At price 22, contribution is 12: 75 copies break even and (900 + 300) / 12 = 100 copies retain the 300 surplus.

CRITICAL CONDITION
Every break-even quantity is verified against revenue and total cost, with whole-copy rounding made explicit.

LIMITS
The model assumes one product and constant unit economics; it is not a forecast or investment recommendation.

This reference is not a learner submission or proof of provider-course completion. See material-verification.json in the production package for actual preparation checks.
