(a) Notwithstanding any other provision of law regarding unwritten contracts, including but not limited to Code Section 13-5-31, a promise to make a contribution to the capital of a limited liability company is not enforceable unless it is set out in the articles of organization or a written operating agreement that is binding on the person to be charged or in another writing signed by that person.

(b) Unless otherwise provided in the articles of organization or a written operating agreement, the obligation of a person to make a contribution to the capital of a limited liability company may be reduced or eliminated only with the unanimous consent of the members.

(c) A written operating agreement may provide that the interest of any member who fails to make any contribution that he or she is obligated to make shall be subject to specified penalties for, or specified consequences of, such failure. Such penalty or consequence may take the form of reducing or eliminating the defaulting member's proportionate interest in a limited liability company, subordinating his or her limited liability company interest to that of nondefaulting members, a forced sale of his or her limited liability company interest, forfeiture of his or her limited liability company interest, the lending by other members of the amounts necessary to meet his or her commitment, a fixing of the value of his or her limited liability company interest by appraisal or by formula and redemption or sale of his or her limited liability company interest at such value, or other penalty or consequence.