The food calorie, equal to 4186J , is a measure of how much energy is released when food is metabolized by the body. A certain brand of fruit-and-cereal bar contains 140 food calories per bar. If a 69.0kg hiker eats one of these bars, how high a mountain must he climb to "work off" the calories, assuming that all the food energy goes only into increasing gravitational potential energy?

If, as is typical, only 20.0% of the food calories go into mechanical energy, what would be the answer to part (a)?