In the R-4 residential zone, minimum area requirements are as follows:

    A.    For each residential building: six thousand five hundred (6,500) square feet, plus one thousand five hundred (1,500) square feet for each dwelling unit in excess of one (1) in each building;

    B.    For other main buildings: seven thousand five hundred (7,500) square feet. (PZSC § 03-22-004)