Unless otherwise provided in the subscription agreement:

    (a) A subscription for shares or for membership made before or after formation of a corporation shall be paid in full at the time, or in installments and at the times, as the board determines.

    (b) A call made by the board for payment on subscriptions is ratable as to all shares or members of the same class.

    (c) A corporation may retain a security interest in any shares or memberships as security for performance by the subscriber of the subscriber's obligations under a subscription agreement and subject to the power of sale or rescission on default provided in section 309.