(1) In addition to the continuation of the sales finance charge or loan finance charge on a delinquent installment with respect to a nonprecomputed consumer credit sale or consumer loan, refinancing or consolidation, repayable in installments, the parties may contract for a delinquency charge on any installment not paid in full within ten days after its scheduled due date of five percent of the unpaid amount of the installment, not to exceed $30.
