1.  Written designation by customer.  Before a repair facility begins repairing a customer's motor vehicle, the customer may designate in writing a specific amount of charges for repair in excess of which the customer does not agree to be liable without further specific agreement, either oral or written.  

2.  No liability without agreement.  A customer is not liable for a charge in excess of the specific amount designated in accordance with subsection 1 without further specific oral or written agreement. A repair facility shall charge a customer by using the same labor rate per hour and shop supplies calculation as is used in any estimate the repair facility provides.  

3.  Shop supplies.  A repair facility may bill for shop supplies calculated as a percentage of labor or by other calculation, if disclosed to the customer, as a single line item.