Final answer:
Portable fire extinguishers with a gross weight of less than 40 pounds must be installed at a specific height.
Step-by-step explanation:
The question is about the installation height of portable fire extinguishers. According to regulations, fire extinguishers with a gross weight of less than 40 pounds should be installed so that the top of the extinguisher is not located more than a certain distance above the floor. Unfortunately, the specific distance is not provided in the question, so it cannot be answered accurately.