A class room measuring 10 m (L) 8 m (B) 2.7 m (H) requires an illumination level of 500 lux on the desk level using 40 W fluorescent lamps with rated output of 5000 lumens each. Assuming utilization factor of 0.5 and maintenance factor of 0.8, the number of lamps required is _________

• A. 20
• B. 40
• C. 80
• D. 120