Did Superior’s October delivery breach the contract?

R. J. Sanders, Inc., had a contract with the federal government to install the heating system at a federal prison camp. The company negotiated with Superior Boiler Works to purchase three large commercial units. On March 27, Superior sent a proposal to Sanders, offering to sell three boilers for a total of $156,000 and estimating time of delivery at four weeks. The parties exchanged further documents and held various discussions. Finally, on July 20, Sanders sent a “purchase order” for three boilers, agreeing to pay $145,827 and stating “Date required: 4 Weeks,” that is, August 20. On August 6, Superior sent a “sales order,” agreeing to sell the three boilers at that price, but providing a shipping date of October 1. This later delivery date forced Sanders to rent temporary boilers at a cost of $45,315. On October 1, Superior shipped the boilers, which arrived on October 5. Sanders sent a check in the amount of $100,000, claiming that Superior had delivered the boilers late and deducting the cost of its rental equipment. Superior sued for the additional $45,000 and moved for summary judgment, which the trial court granted. Sanders appealed, claiming that the contract had required Superior to deliver the boilers within four weeks.