A closed box is filled with dry ice at a temperature of -83.0 oC, while the outside temperature is 22.8 oC. The box is cubical, measuring 0.258 m on a side, and the thickness of the walls is 4.20 × 10-2 m. In one day, 3.09 × 106 J of heat is conducted through the six walls. Find the thermal conductivity of the material from which the box is made.