(1) The department of human services shall assess against the patient, spouse, or parents made liable by section 27-92-101, or any of them, all or such part of the cost as they are respectively able to pay, but the department of human services shall not assess against the liable persons in the aggregate more than the whole of such cost.
(2) The liability of each parent shall cease when such parent has completed the payments as assessed in this article or upon the patient's eighteenth birthday, whichever event first occurs.