In Challenge-Cook Bros., Inc. v. Lantz (1967) 256 Cal.App.2d 536, the guarantor contended there was no consideration for the guaranty, which he claimed was executed three weeks after the lease was signed. The record was "silent" as to when and how the lease and guaranty were signed. (Ibid.) Based on the lack of evidence, the presumption of consideration arising from the guaranty being in writing, and the guarantor's failure to sustain his burden to prove a lack of consideration, the appellate court concluded the trial court's finding that the guaranty was supported by consideration could not be reversed. (Id. at p. 540.)