What percentage of each floor is not usable according to the information provided?

To determine the percentage of each floor that is not usable, it's important to understand the concept of usable square footage in real estate. Usable space typically refers to areas within a building that can be occupied or utilized for activities, excluding spaces such as hallways, elevators, stairwells, and amenities. If the information provided indicates that a specific percentage of each floor is designated as unusable space, then this value is critical in assessing the overall efficiency of the floor's design.

In this case, if the correct answer identifies 20% as the percentage of a floor that is not usable, it indicates that a significant portion is allocated to spaces that do not contribute to the effective use of the floor. This means that out of the total area, 80% is available for actual use, which aligns with the typical practices in building design and real estate assessment. Such calculations are vital for agents, architects, and property managers when analyzing the viability and functionality of a space, as well as for potential tenants or buyers evaluating the area they would be occupying.

This understanding emphasizes the importance of distinguishing between usable and non-usable space, as it has direct implications on valuation and operational efficiency in real estate transactions.