I agree with you that it isn't a very reasonable assumption, I held it on the basis that I was unsure how to approach the question from any other angle. I believe the question refers to the average pressure, this question was posed in a worksheet from my teacher.
The second part of the question...
I assumed that the same magnitude of force acts on all sides of the box. Since A had the smallest area, I ranked P(A) as having the largest pressure, followed by P(B) having the second largest and P(top) and P(bottom) having the same pressure at third largest each. However, the ranking I...