Complicated Machinery Ltd. manufactures and assembles heavy equipment for industry. It accepted an order from Northern Paper Co. for a large machine that would automate certain processes. A term of the order was that the machine was to be delivered by October 31. The manager of Northern Paper Co. had written in a letter accompanying the offer: "Until the machine is in full operation it is hard to say what our savings will be. A thousand dollars a week is a rough guess."

Complicated Machinery Ltd. failed to deliver until December 26, eight weeks late. It billed Northern Paper Co. for the full price less $8000 (eight weeks at $1000 per week). Northern Paper Co. discovered that the machine actually saved $3000 weekly in production costs. It therefore tendered as payment the full price less $24 000 (eight weeks at $3000 per week). Complicated Machinery Ltd. sued Northern Paper Co. Is it Unjust Enrichment case? if so, what is the remedy?