[5] On appeal, the defendants Amstar, Jain and Batt-Rawden confined their submissions to challenging the judgment at trial in favour of the Benson companies, which was for a sum of $72,605.75, consisting of $59,431.50 plus interest at 9% amounting to $13,174.25. The principal sum for which judgment was given included the amount of $21,000 mentioned in the letter of 9 April 2001 for which liability is disputed on appeal. In other respects, the quantum of the amount for which judgment was given against Amstar and against Jain and Batt-Rawden on their guarantees has not been questioned on the appeal. The appellants do, however, deny liability for it on several grounds. Essentially their submissions are that there was no lease or tenancy, either because its terms were uncertain or because it was subject to the execution of a formal instrument of lease that was never signed; that, for that reason also, no guarantee was in fact given by the two individual defendants; and that the amount of $21,000 never became due and payable, the tenancy having been terminated not in the terms of the letter of 9 April 2001 by Amstar, but by the Benson companies themselves. It is acknowledged in their written outlines that each of these issues involve construction of the correspondence and a consideration of the surrounding circumstances. The findings of the learned trial judge on credibility, which went in favour of the plaintiff's witnesses, have not been challenged on appeal.