$ = \frac{1}{{80}} \times 0.2 \times 4 \times \frac{{(100 - 0)}}{{\sqrt 4 }} \times 10 \times 60$
$ = \frac{{0.2 \times 4 \times 100 \times 600}}{{80 \times 2}} = 300\;gm$


Taking the thermal conductivity of Ice as ${K}$, and its specific latent heat of fusion as $L$, the rate of Increase of the thickness of ice layer, at this instant would be given by