In Subdistrict C, and in Subareas D1, D2, and D3, for zoning lots containing schools regulated by Section 139-214 (Special floor area provisions for zoning lots containing schools), the maximum tower height specified by the regulations in this Section, inclusive, may be increased as-of-right by 40 feet. This allowance may be further modified by the provisions of Section 139-47 (Authorization for sites containing schools).