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Solution :

Assuming that heat loss from the sides of the slab is negligible, the amount of heat flowing through the slab is <br> `Q=(kA(T_1-T_2)t)/(d)` ..(i) <br> If m is the mass of ice and L the latent heat of fusion, then <br> `Q=mL` ..(ii) <br> From Eqs. (i) and (ii) we have <br> `mL=(kA(T_1-T_2)t)/(d)` <br> or `k=(mLd)/(A(T_1-T_2)t)` ..(iii) <br> Given `m=4.8kg`,`d=10cm=0.1m`,`A=3600cm^2=0.36m^2` <br> `T_1=100^@C`,`T_2=0^2C` and `t=1h=(60xx60)s` <br> We know that `L=80 cal//g=80000cal//kg=80000xx4.2J//kg=3.36xx10^5J//kg` <br> Substituting these values in Eq. (iii) and solving, we get <br> `k=1.24J//s//m^@C` or `1.24W//m//K`