A 5cm thick ice block is there on the surface of water in a lake. The temperature of air is ?10°C; how much time it will take to double the thickness of the block (L = 80 cal/g, Kicc = 0.004 Erg/s-k, dice = 0.92 g cm?3) [RPET 1998]

• A.            1 hour                                     
• B.            191 hours
• C.            19.1 hours                             
• D.            1.91 hours