You are designing a high-speed elevator for a new skyscraper. The elevator will have a mass limit of 2400 kg (including passengers). For passenger comfort, you choose the maximum ascent speed to be 18 m/s, the maximum descent speed to be 10 m/s, and the maximum acceleration magnitude to be 1.2 m/s². Ignore friction. 

(a) What are the maximum and minimum upward forces that the supporting cables exert on the elevator car? 

(b) What is the minimum time it will take the elevator to ascend from the lobby to the observation deck, a vertical displacement of 640 m? 

(c) What are the maximum and minimum values of a 60 kg passenger's apparent weight during the ascent? 

(d) What is the minimum time it will take the elevator to descend to the lobby from the observation deck?