The city of Calgary advertised for tenders for a construction project. One of the terms of the advertisement was that once submitted, the bid could not be revoked. Northern Construction submitted a low bid on the job. They then examined their bid and realized they had made an error in their calculations. They showed these documents to Calgary's representatives who agreed that they had made an error. Northern Construction then requested that they be released from their bid. Calgary, however, would not release them from the bid and then accepted it as the winning one. Northern Construction refused to honour the contract and Calgary was forced to go with the second lowest bid. They then sued. Explain the legal arguments available to both sides and the likely outcome of the action.