Where the trader has not reimbursed the sums paid by the consumer, the sums due shall automatically be increased by the statutory rate of interest if the reimbursement is made no later than ten days after the expiry of the periods laid down in the first and second paragraphs of Article L. 221-24, of 5% if the delay is between ten and twenty days, of 10% if the delay is between twenty and thirty days, of 20% if the delay is between thirty and sixty days, of 50% between sixty and ninety days and of five additional points per new month of delay up to the price of the product, then of the legal interest rate.