Where a budget session is attended by an effective majority of the public body, it is required to be open to the public. Where a budget session is attended by less than a quorum or effective majority, it is not required to be open to the public unless the group or committee has effective authority to act on portions of the budget or to prevent certain budget items from coming before the public body. See N.J.S.A. 10:4-8b and c; Atty. Gen. Formal Op. 1976, No. 19.