A single lamp placed centrally at the roof provides 40 lux illumination vertically below, at the floor of an underground workshop. The workshop of dimensions 20 m × 20 m with height 4m. Assuming uniform spherical dispersion of luminous intensity, the floor level illumination in lux at any corner of the workshop is

A. 23.2

B. 10.9

C. 3.0

D. 0.8

Answer: Option D