On May 28, 2014, after the construction was more than half completed, the cost of bricks used for construction of the building increased substantially in the marketplace so that Contractors could no longer construct the building for $5,000,000. Contractors told College that it would need an additional $250,000 to complete the building using gray bricks on the exterior.
This situation is common in construction contracts.
What legal contract law doctrine/defense could Contractors use to justify its request for additional money to complete the project?