15. Yost Corp., a computer manufacturer, contracted to sell 15 computers to Ivor Corp., a computer retailer. The contract specified that delivery was to be made by truck to Ivors warehouse. Instead, Yost shipped the computers by rail. When Ivor claimed that Yost did not comply with the contract, Yost told Ivor that there had been a truckers strike when the goods were shipped. Ivor refused to pay for the computers. Under these circumstances, Ivor A. Is obligated to pay for the computers because Yost made a valid substituted performance. B. May return the computers and avoid paying for them because the contract was void under the theory of commercial impracticability. C. Is obligated to pay for the computers because title to them passed to Ivor when Ivor received them. D. May return the computers and avoid paying for them because of the way Yost delivered them