Imagine a beachside changing area with several partial-height partitioned stalls that allow beachgoers to change clothes in relative privacy. These partitions are arranged in two parallel rows, back to back, with an aisle in between for people to walk. Each changing stall is made of three walls and a curtain in the front that can be drawn for complete privacy from the front view. However, the stalls have no ceilings and the partitions only extend about 6 feet high, leaving a gap between the partition tops and the typical adult's full standing height.

In one such stall, there is Kofi who is 6 feet 2 inches tall. He's in a stall in the middle of one row and has drawn the curtain for privacy, but due to his height, his head and shoulders are visible above the partition. Directly across the aisle in the opposite row of stalls, XiuYing, who is 5 feet 6 inches tall, is trying on a new swimsuit. The curtain of her stall is also drawn closed. On XiuYing's right, two stalls over, is Alejandro, a 5 feet 9 inches tall gentleman who is putting on his sunblock. 

Consider that this aisle is quite narrow, only allow one person to pass at a time, and that on the open side of the aisle, facing Kofi's stall, there is a tall mirror mounted on the wall, angled downward. This mirror is intended for people to see their full outfit after changing. 

The question involves what each person can see given their positions and the properties of the stalls. Specifically, what can Kofi see of XiuYing and Alejandro from his position given that he towers above the partition? From her own stall, can XiuYing, who stands shorter than the partition walls, see Kofi or Alejandro above the partition? And what can Alejandro see or infer about his surroundings while applying his sunblock?
Starting with Kofi, his head and shoulders extend above the 6-foot-tall partition due to his height. Since the partitions have no ceiling, Kofi has a vantage point that allows him to see over the partitions into the stalls directly across from him as well as possibly into neighboring stalls depending on how close they are and the angle of view. However, considering the privacy curtain is closed, he would not be able to see directly into XiuYing's stall across from him. Kofi may catch glimpses of movement from stalls adjacent to him if people are moving around in such a way that their hands or other objects extend above the partition height. 

XiuYing, at 5 feet 6 inches tall, cannot see directly into other stalls from within her own because the partitions are taller than she is. She cannot see Kofi or Alejandro over the partition. However, because there is a mirror on the wall, angled downward, she could potentially see the reflection of Kofi's head and shoulders if she is standing in the right position to see into the mirror. She would not see Alejandro this way because he is two stalls down and the angle of reflection is unlikely to provide a clear line of sight.

Alejandro, while shorter than the partition, has limited visibility towards the other stalls directly. He will not be able to see Kofi directly due to the partition height. However, he could potentially infer the presence of someone taller like Kofi if he notices the top of someone's head or shoulders above the partition, or even his own reflection in the angled mirror when he stands close enough to the aisle. He cannot see XiuYing as she is shorter than the partition walls and her stall curtain is closed.

As for what they could infer about each other's presence, auditory and visual cues such as shadows moving beneath the partition gaps, or sounds of rustling clothes or curtain movement, can inform them of activity within neighboring stalls, but without specific height-related visual information, they would rely on indirect knowledge of each other's presence.