Answer:
the luminous ceiling MUST be highly reflective (white)
Explanation:
Different illumination systems can be selected for different areas of the building. In a merchandise area, mostly in a pharmacy, the electrician needs to make the illumination system to be efficient by making the surfaces above the luminous ceiling to be highly reflective white. This illumination set-up would be part of the conditions necessary for visual comforts to be attained in those areas at all times.