Central Land Development Ltd. sold three commercial building lots to Commercial Builders Ltd. for the sum of $400,000. As a part of the purchase price, Perros and Masson, the two principal shareholders of Commercial Builders Ltd., and the corporation gave Central Land Development Ltd. a mortgage for $250,000. The balance of the $400,000 selling price, in the amount of $150,000 was paid at the time of the purchase. A year and six months later, Commercial Builders Ltd., and its two shareholders wished to pay off the mortgage, and requested Central Land Development Ltd. to provide them with a pay-out amount. Central Land Development Ltd. requested its accountant, Hamilton, to calculate the balance owing on the mortgage. Hamilton calculated the balance owing to be $172,459. Commercial Builders Ltd. paid the amount and received a discharge of the mortgage. Several months later, Central Land Development Ltd. discovered that the amount calculated by Hamilton was in error, and the correct balance was in fact $202,459. Central Land Development requested payment from Commercial Builders Ltd. of the $30,000 difference, but Commercial Builders Ltd. refused to pay the amount. Discuss the issues raised in this case, and the arguments that might be raised by each of the parties.