Key legal question
Whether the cantonal finding that 10% interest was agreed only for the first year was arbitrary
Extracted holding
The finding was not arbitrary; the signed acknowledgment supported only one year of 10% interest, after which statutory default interest applied.
Extracted reasoning
The acknowledgment expressly included CHF 800 interest in the total, which made sense only if one year's interest was meant. The unsigned sheet was not binding and did not make the cantonal interpretation manifestly untenable.