A small pond of depth 0.5 m deep is exposed to a cold winter with...

A small pond of depth 0.5 m deep is exposed to a cold winter with outside temperature of 263 K . Thermal conductivity of ice is $K=2.2 \mathrm{Wm}^{-1} \mathrm{~K}^{-1}$, latent heat $L=3.4 \times 10^5 \mathrm{Jkg}^{-1}$ and density $\rho=0.9 \times 10^3 \mathrm{kgm}^{-3}$. Take the temperature of the pond to be 273 K . The time taken for the whole pond to freeze is about