As a condition of final subdivision or site plan approval, the Municipal Agency may require an applicant to pay his/her pro rata share of the cost of providing reasonable and necessary circulation improvements and drainage facilities, including land and easements, located off-tract of the property limits of the subdivision or development but necessitated or required by the development. "Necessary" improvements are those clearly, directly, and substantially related to the development in question. The board shall provide in its resolution of approval the basis of the required improvements. The improvements cost shall include all design, legal, and the related expenses. The proportionate or pro rata amount of the cost of such facilities within a related or common area shall be based on the following criteria.