A contractor entered into an agreement with a homeowner whereby the contractor would construct a fireplace in the homeowner's home for a fee of $5,000, with construction set to begin in July and to be finished by October 1. The contractor began the work promptly but soon found that the walls of the homeowner's home were built more solidly than expected, which was particularly unusual for homes in the homeowner's neighborhood. The contractor notified the homeowner immediately of the problem with the walls. The contractor told the homeowner that in order to build the fireplace as planned; it would cost an extra $1,500 in labor and materials. Because the homeowner needed the fireplace ready in time for the winter, he agreed, albeit reluctantly, to the increase. The contractor completed the work on September 29.

Under the modern rule, what amount must the homeowner pay the contractor?