Computers, Inc., contracted in writing with Bank to sell and deliver to Bank a mainframe computer using a new type of magnetic memory, then under development but not perfected by Computers, at a price substantially lower than that of a similar computer using current technology. The contract's delivery term was "F.O.B. Bank, on or before July 31." Assume that Computers tendered the computer to Bank on August 15, and that Bank rejected it because of the delay. If Computers sues Bank for breach of contract, which of the following facts, if proved, will best support a recovery by Computers? 
The delay did not materially harm Bank. Computers believed, on the assumption that Bank was getting a "super deal" for its money, that Bank would not reject because of the late tender of delivery.  Computers' delay in tender was caused by a truckers' strike. A usage in the relevant trade allows computer sellers a 30-day leeway in a specified time of delivery, unless the usage is expressly negated by the contract. 