X Co. is a retail dealer of garden tractors. Mr. Y signs a contract to buy a garden tractor for $400 but later backs out of the agreement. The tractor that Y agreed to buy is subsequently sold to Mr. Z for $380. The average cost of a garden tractor to X co. is $260, and the average variable cost is $220. The marginal cost to X co. of supplying an additional tractor to a customer is $300.
X Co. sues Y for breach of contract. How much damages should be awarded to X co? You must explain your answer to get any credit.