If a county requires the relocation or removal of a Commission facility, the county shall give notice to the Commission of the requirement within a reasonable time. On receiving notice, the Commission shall provide the county with an estimate of the cost of removing or relocating the facility. On completion of the removal or relocation of the facility, the Commission shall provide the county with an itemized statement of the actual cost of removal or relocation. For the relocation or removal of a facility for which the Commission is required to pay because of any road construction or improvement required by either Montgomery County or Prince George’s County, the governing body of the county in which the construction or improvement is made shall pay one–half of the actual cost of the construction or improvement in that county. Unless the county disputes a charge in the itemized statement of actual costs, the county shall pay the costs within 6 months after receipt of the statement. If the itemized statement as submitted or finally agreed on is not paid within 6 months after submission or agreement, the itemized statement shall bear 6% interest until paid. If there is a dispute over a charge in the itemized statement of actual costs, within 3 months after receipt of the statement, the dispute shall be referred to an arbitrator selected by the Commission and the county. If the Commission and the county do not agree on an arbitrator, the Commission and the county shall each appoint an arbitrator, who jointly shall appoint a third arbitrator. If a dispute goes to arbitration, the itemized statement as finally determined shall bear 6% interest after 6 months from the date of the finding by the arbitrator or arbitrators until the statement is paid.