Heat engines take input energy in the form of heat, use some of that energy to do work, and exhaust the remainder. similarly, a person can be viewed as a heat engine that takes an input of internal energy, uses some of it to do work, and gives off the rest as heat. suppose a trained athlete can function as a heat engine with an efficiency of 0.10. (a) what is the magnitude of the internal energy that the athlete uses in order to do 1.5x104 j of work? (b) determine the magnitude of the heat the athlete gives off.