A drawing hall 36 m x 20 m is to be illuminated to get an illumination of 20 candles per square meter on a working plane. Assuming space-height ratio as 1.3, mounting height as 3 m, utilization factor as 0.5, depreciation factor as 0.75, and 80 W tube light lamp efficacy as 40 lm/W, calculate the number of lamps, wattage of each lamp, and their disposition.