Most of the energy we consume as food is converted to thermal energy in the process of performing all our bodily functions and is ultimately lost as heat from our bodies. Consider a person who consumes 2100 kcal per day (note that what are commonly referred to as food calories are actually kilocalories), of which 2000 kcal is converted to thermal energy. (The remaining 100 kcal is used to do work on the environment. The person has a surface area of 1.8 m² and is dressed in a bathing suit.

  (a) The person is in a room at 20°C, with a convection heat transfer coefficient of 3 W/m². K. At this air temperature, the person is not perspiring much. Estimate the person's average skin temperature.

  (b) If the temperature of the environment were 33°C, what rate of perspiration would be needed to maintain a comfortable skin temperature of 33°C?