; (B) calculation and application of differing share prices as between redeeming and purchasing shareholders; (C) adoption, calculation, or use of mandatory fees on shareholder transactions or transacting shareholders; or (D) adoption or use of any measures economically similar to the foregoing. (2) Rule of construction Nothing in this subsection may be construed to prevent a registered open-end company from voluntarily adopting any measure described under subparagraph (A) through (D) of paragraph (1). .