EM waves

If 2.5 $\times 10 -$6 N average force is exerted by a light wave on a non-reflecting surface of 30 cm 2 area during 40 minutes of time span, the energy flux of light just before it falls on the surface is ___________ W/cm 2 . (Round off to the Nearest Integer) (Assume complete absorption and normal incidence conditions are there)

Integer / Numeric Answer Type

Enter your answer as a number (integer or decimal).