An icebox made of 1.5cm thick stuyrofoam has dimensions `60cmxx60cmxx30cm.It contains ice at which the ice is melting. Latent heat of fusion of ice`=3.36xx10^(5)J kg^(-1)` . and thermal conductivity of styrofoam `=0.04Wm^(-1)`^(@)C^(-1)` .

Explanation

The total surface area of the walls `=2(60cmxx60cm+60cmxx30cm+60cmxx30cm)` . `=1.44m^(2)` . The thickness of the walls `=1.5cm=0.015m`
The rate of heat flow into the box is. `(DeltaQ)/(Deltat)=(KA(theta_(1)-theta_(2)))/(x)` . `=((0.04Wm^(-1)`^(@)C^(-1))(1.44m^(2))(40^(@)C))/(0.015m)=154W` . The rate at which the ice melts is `=(154W)/(3.36xx10^(5)J kg^(-1)=0.46g s^(-1)` .