Water inside a stainless steel spherical vessel of 1 m inner diameter and 10 mm wall thickness, is maintained at 50^o C. The exterior surface of the vessel is exposed to ambient air (T? = 25^o C). Assume the external convection heat transfer coefficient to be 6 W/m2K, and the conductivity of stainless steel is k_ss = 17 W/mK. Assume the inner surface of the vessel is also at 50^o C. Which of the following values is closest to the heat loss from the vessel? 

A). 100 W 

B). 500 W 

C). 1000 W 

D). 2000 W