Liquid nitrogen at 77 k is stored in an insulated spherical vessel that is vented to the atmosphere. the container is made of a thin-walled material with an outside diameter of 0.5 m; 25 mm of insulation (k = 0.002 w / m k) covers the outside surface. the latent heat of nitrogen is 200 kj/kg and its liquid phase density is 804 kg/m3. for surroundings at 25oc and a convective heat transfer coefficient (h = 18 w / m2) at the outside surface of the insulation, what is the rate of liquid nitrogen boil-off? report your answer in cm3 (of liquid)/hr.