A winter hiker’s body generates heat at a rate up to a maximum value of 120 W. She is hiking on a brisk day in which the outdoor temperature is -10°C, while wearing a jacket with goose down insulation. How thick must the jacket be so that she can maintain a normal body temperature? Assume her surface area for heat flow (the jacket) is 1.5 m² and that all of her body heat flows out through the jacket.