Health care insurers may place reasonable limits on the number of classes of preferred providers which satisfy the standards set forth by the health care insurer, provided that there be no discrimination against any providers on the basis of religion, race, color, national origin, age, sex, or marital status, and further provided that selection of preferred providers is made on the combined basis of least cost and highest quality of service.
N.D.C.C. § 26.1-47-04