The freezer compartment in a conventional refrigerator can be modeled as a rectangular cavity 0.3 m high and 0.25 m wide with a depth of 0.5 m. Determine the thickness of styrofoam insulation (k = 0.30 W/m · K) needed to limit the heat loss to 400 W if the inner and outer surface temperatures are -10 and 33°C, respectively.