Broker needed a certain rare coin to complete a set that he had contracted to assemble and sell to Collecta. On February 1, Broker obtained such a coin from Hoarda in exchange for $1,000 and Broker's signed, written promise to re-deliver to Hoarda "not later than December 31 this year" a comparable specimen of the same kind of coin without charge to Hoarda. On February 2, Broker consummated sale of the complete set to Collecta. On October 1, the market price of rare coins suddenly began a rapid, sustained rise; and on October 15 Hoarda wrote Broker for assurance that the latter would timely meet his coin-replacement commitment. Broker replied, "In view of the surprising market, it seems unfair that I should have to replace your coin within the next few weeks." 177. For this question only, assume the following facts. Having received Broker's message on October 17, Hoarda sued Broker on November 15 for the market value of a comparable replacement-coin as promised by Broker in February. The trial began on December 1. If Broker moves to dismiss Hoarda's complaint, which of the following is Broker's best argument in support of the motion? 
Broker did not repudiate the contract on October 17, and may still perform no later than the contract deadline of December 31.  Even if Broker repudiated on October 17, Hoarda's only action would be for specific performance because the coin is a unique chattel.  Under the doctrine of impossibility, which includes unusually burdensome and unforeseen impracticability, Broker is temporarily excused by the market conditions from timely performance of his coin-replacement obligation.  Even if Broker repudiated on October 17, Hoarda has no remedy without first 17, Hoarda has no remedy without first demanding in writing that Broker retract his repudiation. 