Deal-cost model for supplier negotiation (CentriComp)

Problem

Comparing supplier offers on nominal price alone hides what a deal really costs: when payments fall due, which service package is included, when installation happens, how much solvent is recycled and the disposal liability left behind. In the ITLS6202 CentriComp case, the buyer had to judge a supplier's offer for a solvent recycling acquisition against a baseline on a like-for-like basis.

Approach

1. I designed the deal-cost model and built the app myself: each negotiation lever (nominal price, payment schedule, service package, installation timing, solvent recycling rate and disposal cost) feeds a present-value net cost compared with the baseline.
2. I isolated the model logic in pure functions, separate from the React interface, so every figure on screen comes from testable code.
3. The interface shows a verdict gauge against the baseline, a waterfall from sticker price to net cost, the maximum break-even price for each payment plan and an A/B/C scenario comparison.
4. From the current inputs, the app computes a negotiation playbook and raises a sustainability flag when toxic solvent is left unrecycled.
5. I covered the model with 13 Vitest unit tests, including a 5,184-case check that the break-even price always returns zero versus baseline, then rebuilt, fixed and deployed the app on Netlify.
6. All inputs are case assumptions; the app makes no claim about grades, savings or real negotiation outcomes.