The conditions and limitations established in this section apply to contracts or amendments to contracts entered into under this subtitle to acquire parkland in the metropolitan district in accordance with § 1(a) and (b) of the Capper–Cramton Act, Public Law 71–284, 46 Stat. 482. Except as provided in subsection (d) of this section, the Commission may amend a contract. An amendment to a contract shall be ratified by the appropriate county council before the amendment becomes binding on the State, the Commission, or the county. The Commission may enter into a contract with a governmental unit to: adopt a general or revised plan for the acquisition of parklands in the metropolitan district; and specify the method to finance the acquisition. The appropriate county council shall ratify a contract before the contract becomes binding on the State, the Commission, or the county. The Commission may enter into a supplemental agreement to a contract or amendment to a contract with a governmental unit in accordance with this subsection. A supplemental agreement shall: be for the acquisition of specific units of land in the metropolitan district that comprise portions of the general park plan adopted in the contract or amendment to the contract; and specify the financing for the acquisition. A supplemental agreement for a specific unit of land located in Montgomery County or Prince George’s County shall be submitted to the appropriate county council for ratification. The appropriate county council shall ratify a supplemental agreement if the county finds that: the boundaries of the unit of land to be acquired under the supplemental agreement are in the general park plan adopted by the contract or amendment that the agreement supplements; and the proceeds from the taxes authorized under the supplemental agreement will allow the Commission to satisfy the obligations of the supplemental agreement, including any interest. In determining whether the Commission will be able to meet an obligation with the proceeds of the taxes authorized under the supplemental agreement, the appropriate county council shall: compute the proceeds on the assessable basis of the parts of the metropolitan district lying in the county for the fiscal year in which approval is sought; and assume that the entire tax imposed will be collected so long as there is an outstanding and unpaid obligation. The appropriate county council may ratify the supplemental agreement by simple resolution authorizing the chair of the county council to: endorse the supplemental agreement; and execute a guarantee in accordance with this subtitle. Ratification by the Montgomery County Council is not necessary to approve: contracts or amendments that are not related to the acquisition of a specific unit of parkland; or supplemental agreements to contracts related only to the acquisition of specific units of parkland.