(a) Whenever the area of adequate school construction existing in an attendance area is less than the maximum area computed for that attendance area, any portion of the remaining computed allowable building area may be used for the construction of district administration and maintenance facilities.
(b) If the allowable building area is computed separately by attendance area, the board shall include within the computation of the maximum area for that attendance area the proposed building area of a project for the construction of district administration and maintenance facilities.