QUESTION 4 Calculate the monthly (30 days) electricity account of a block of flats, for which the following data is known. This 20 story high rise complex has 180 units. It is assumed that each unit uses an average of 385 kW.h per month. This upmarket complex also has a swimming pool and sauna. The swimming pool draws 17,5 A, single phase, when it is supplied with 225 V at 50 Hz. The pool pump is used for 12 hours per day. The sauna operates five hours per day and it is rated at 3 kW. These premises also have 2 elevators. It is estimated that each elevator does an average of 5 upward trips per hour, each average trip of 25 seconds has four people with a total mass of 250 kg that it lifts through a height of 35 m. The rope mechanism of the lifts has an efficiency of 98 %. The motors driving the lifts are only 85 % efficient. The passage, lobby and outside lights add another 750 kW.h per month. Use 49 c/kW.h. HINT: Use only the upward trips of the lifts, ignore the downward trips. [8]