Koa contracts to ship one hundred cases of Fresh Niblets brand corn to Allman of Dayton, Ohio by way of National Truck Lines on October 2, FOB Dayton at $25 per case. Allman is to make a ten percent down payment. The payment is to be received at Koa's place of business before shipment occurs. Koa ships the corn on October 2, although she has not yet received the down payment, and the goods arrive in Dayton. There they remain in National's truck. Because Allman has failed to make the down payment, Koa orders National not to take the goods to Allman's warehouse. Allman claims that at this point Koa has no right to take back the corn. Discuss Koa's rights and the validity of Allman's argument.