Final answer:
The time required for the crates to return to their initial positions is longer when using the elevator first compared to sliding it on the third floor due to a higher coefficient of kinetic friction.
Step-by-step explanation:
The question asks to rank the time required for the crates to return to their initial positions from largest to smallest. Since we're analyzing the time required, we can refer to the information given in exercise 90. The work needed by the workers to bring the crate from site A to site E via the elevator is the same as the work needed to slide the crate on the third floor from C to E.
However, the coefficient of kinetic friction between the crate and the third floor is higher than that between the crate and the ground floor. Therefore, it would take longer for the crate to return to its initial position when using the elevator first compared to sliding it on the third floor.