(a) Unless the organic rules otherwise provide, voting by a proxy at a members meeting shall be prohibited. This subsection shall not prohibit delegate voting based on district or class. (b) If voting by a proxy is permitted, a patron member shall appoint only another patron member as a proxy and, if investor members are permitted, an investor member shall appoint only another investor member as a proxy. (c) The organic rules may provide for the manner of, and provisions governing, the appointment of a proxy. (d) The organic rules may provide for voting on any question by ballot delivered by mail or voting by other means on questions that are subject to vote by members.