The radiative heat transfer rate per unit area (W/m$$^2$$) between two plane parallel grey surfaces (emissivity = 0.9) maintained at 400 K and 300 K is (Stefan Bottzman constant
$$\sigma = 5.67 \times 10^{-8} W/m^2 K^4$$)

A

992

B

812

C

464

D

567