Where a borrower negotiates an extension of a loan repayment date and agrees to pay interest at a specified rate as the price for obtaining that extension, the interest obligation is a primary stipulation — being the consideration for the grant of new rights — and does not engage the doctrine of penalties, even if the rate is described as a 'Default Rate' and even if the underlying loan agreement contained a separate default interest provision that may have engaged the penalty doctrine. The substance of the variation contract, not the labels used, determines whether the stipulation is primary or collateral.
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