It is important for the body to have mechanisms to effectively cool itself. If not, moderate exercise could easily increase body temperatures to dangerous levels. Suppose a 70 kg person runs on a treadmill for 30 min, using a metabolic power of roughly 1 kW while they run. Assume for simplicity that all of this power ultimately goes into thermal energy generated by the body that increases the body's temperature

The previous problems show that given how much heat the human body generates, it's crucial for its survival to have effective mechanisms to cool itself. One such mechanism is sweat. When a person sweats, water on the surface of the skin absorbs heat from the body and evaporates - it goes directly from liquid water at skin temperature to water vapor. The heat of vaporization at human skin temperature is about 0.66 kWh/kg. For the runner specified in the problem statement, how many liters of water need to be evaporated from their skin over the course of one hour to keep their body temperature constant if sweating were the only form of cooling their body?