An insulated cardboard box is to be designed to transport a labile vaccine product that has to be kept at −78°C in areas where lowtemperature refrigeration is not widely available. The box is a cube 0.3 m on a side and is filled halfway with dry ice, which keeps the contents cold by slowly subliming. The box will be insulated with a layer of Styrofoam insulation (k = 0.030 W/m K). Determine the thickness of insulation needed if the low-temperature has to last for 1 week assuming that the outside temperature is 30°C and that the heat transfer resistance of the insulation is dominant. Assume that the bulk density of the dry ice is 1,200 kg/m3.