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It is desired to illuminate a drawing hall with an average illumination of about 250 lux. The area of hall is 30 m × 20 m. The lamps are to be fitted at 5 m height. Find the number and size of incandescent lamps required for an efficiency of 12 lumen/watt. Utilization factor = 0.4 and maintenance factor = 0.85. 

 (a) 40 and 1000 W (b) 20 and 500 W (c) 60 and 1000 W (d) None of the above 

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