The food calorie, equal to 4186 J, 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.

(a) If a 65-kg 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?

(b) If, as is typical, only 20% of the food calories go into mechanical energy, what would be the answer to part (a)?