A 4-m-diameter spherical tank contains iced water at 0°C. The tank is thin-shelled and thus its outer surface temperature may be assumed to be same as the temperature of the iced water inside. Now the tank is placed in a large lake at 20°C. The rate at which the ice melts is
(a) 0.42 kg/s

(b) 0.58 kg/s

(c) 0.70 kg/s

(d) 0.83 kg/s

(e) 0.98 kg/s
(For lake water, use k = 0.580 W/m · K, Pr = 9.45, v = 0.1307 × 10^-5 m²/s, β = 0.138 × 10^-3 K^-1)