Any of the following uses when authorized as a special exception: those uses described in § 250-62G as well as offices for professional services, personal services and administrative activities, including sale of products customarily incidental to the uses permitted in this section such as offices of agents, physicians, dentists, lawyers, architects, engineers, musicians, artists, teachers, optometrists and photographers, provided that no office shall occupy more than 20% of the total floor area of the proposed development.