Q. A winter hiker's body generates heat at a rate up to an utmost value of 126 W. She is hiking on a brisk day in which the outdoor temperature is 9 °C, whilst wearing a jacket with goose down insulation. How thick should the jacket be so that she can maintain a normal body temperature? Assume her surface area for heat flow (the jacket) is 1.5m2 and that all of her body heat flows out through the jacket. (Suppose the thermal conductivity to be 0.025 W/m • K.)