A closed box is filled with dry ice at a temperature of -94.2 oC, while the outside temperature is 21.0 oC. The box is cubical, measuring 0.337 m on a side, and the thickness of the walls is 4.11 × 10-2 m. In one day, 3.96 × 106 J of heat is conducted through the six walls. Find the thermal conductivity of the material from which the box is made?