Liquid ammoia at -20C is stored in spherical vessel of inner and outer radius 1m and 1.05 m respectively. The inner shell of 3 cm thick is made of nickel steel (k= 19 W/mK) and the outer shell of thick 2 cm is made of carbon steel (k= 54 W/mK). The vessel is exposed to atmospheric air at 30C. The inside and ouside H.T.C are 100 W/m^2 K and 10 W/m^ 2K, respectively. Calculate the rate of heat losses from liquid ammonia.