If the articles of association or bylaws of a professional association fail to fix a price at which a professional association or its members or shareholders may purchase the membership or shares of a deceased, retired, expelled, or disqualified member or shareholder, and if the articles of association or bylaws do not otherwise provide, then the price for such membership or shares shall be the book value of such membership or shares at the end of the month immediately preceding the death or disqualification of the member or shareholder. Book value shall be determined by an independent certified public accountant employed for such purpose from the books and records of the professional association by the regular method of accounting employed by the professional association. The determination by the certified public accountant of book values shall be conclusive on the professional association and its members or shareholders.