'The interpretation of a statute by an administrative agency charged with the responsibility of enforcing that statute is entitled to judicial deference. This deference is sometimes called the doctrine of operative construction. . . . If there is a rational basis for the agency's interpretation, it should be upheld on judicial review. . . . However, the determination of an administrative body as to questions of law is not conclusive and, while persuasive, is not binding on the courts.' Deference to an agency's interpretation is especially appropriate when 'the agency is one of special competence and experience.' However, the final construction of a statute always rests with the courts.''