4 The population of a 24-storey office building is 300 persons. The building is served by a group of lifts each with a contract speed of 6 m/s. The client intends to achieve an up-peak-interval of not more than 64 s with the expected up-peak demand not less than 20%. The inter-floor height is 6 m. The door opening time is 1.5 s. The door closing time is 1.5 s. The passenger loading time is 1 s. The passenger unloading time is 1 s. The single floor flight time is 5 s. Determine: (a) the minimum up-peak handling capacity (UPPHC); (b) the minimum contract capacity (CC); (2 marks) (2 marks) (c) the average highest call reversal floor (H) and the average number of stops (S); (d) the round-trip time (RTT); (e) the number of lift required; (f) the real up peak interval; (g) the real up peak handling capacity; and (2 marks) (3 marks) (1 mark) (1 mark) (1 mark) (h) the real percentage of population handled. Hence, comment whether the quality of the lift system is top quality office, mid-range or office building of low-end market. (3 marks)