A slab of stone of area 0.36m2 and thickness 0.1m is exposed on the lower surface to steam at 100∘C. A block of ice at 0∘C rests on the upper surface of the slab. In one hour 4.8kg of ice is melted. The thermal conductivity of slab is (Given: latent heat of fusion of ice =3.36×105 J kg–1)