Section 28-7505 - Liability; bond validityA. The members of the board or a person executing the bonds is not personally liable for the payment of the bonds.B. The bonds are valid and binding obligations of the department notwithstanding the fact that before the delivery of the bonds any of the officers whose signatures appear on the bonds cease to be officers of the department.C. From and after the sale and delivery of the bonds, the bonds are incontestable by the board or department.