If a 4 ~kg of ice is inside a closed cubical thermocol box of side length 20 ~cm and wall thickness 4 ~cm then the mass of the ice remaining after 10 hours is nearly (The out side temperature =50^ C co-efficient of thermal conductivity of thermocol =0.01 Js ⁻¹ ~m ^ -1 ^ C ⁻¹ Latent heat of fusion of ice =335 10^3 ~J ~kg ⁻¹ )