{
    uint256 previousInterestRate = loan.perAnumInterestRate;
    uint256 previousDurationSeconds = loan.durationSeconds;

    require(interestRate <= previousInterestRate, 'NFTLoanFacilitator: rate too high');
    require(durationSeconds >= previousDurationSeconds, 'NFTLoanFacilitator: duration too low');

    require((previousLoanAmount * requiredImprovementRate / SCALAR) <= amountIncrease
    || previousDurationSeconds + (previousDurationSeconds * requiredImprovementRate / SCALAR) <= durationSeconds 
    || (previousInterestRate != 0 // do not allow rate improvement if rate already 0
        && previousInterestRate - (previousInterestRate * requiredImprovementRate / SCALAR) >= interestRate), 
    "NFTLoanFacilitator: proposed terms must be better than existing terms");
}
(previousInterestRate != 0 // do not allow rate improvement if rate already 0
        && previousInterestRate - Math.ceilDiv(previousInterestRate * requiredImprovementRate, SCALAR) >= interestRate)
