The profits and losses of a limited liability company shall be allocated among the members, and among classes of members, on the basis provided in writing in the articles of organization or an operating agreement. If the articles of organization or an operating agreement does not so provide in writing, profits and losses shall be allocated on the basis of the value, as stated in the limited liability company records required to be kept pursuant to § 13.1-1028, of the contributions made by each member to the extent they have been received by the limited liability company.