Your company, Acme Widgets, sells its widgets worldwide. Acme has a contract for 250,000 widgets to be shipped to the Czech Republic. The price stated in the offer and acceptance is $1 per widget, C.I.F. Prague. During the production of the widgets, the price of one component increases 250 percent due to a shortage. In addition, these widgets are due for shipment on June 15 and arrival in Prague no later than July 1. On June 15, a stevedores’ strike begins, which lasts for 60 days. Are either or both of these factors—the material price increase and the stevedores’ strike—an excuse for Acme’s nonperformance? What legal theory might Acme use under U.S. common law as an excuse? Under the CISG?