The food calorie, equal to 4186 j, is a measure of how much energy is released when the body metabolizes food. a certain fruit­and­cereal bar contains 140 food calories. (a) if a 65­kg hiker eats one bar, how high a mountain must he climb to "work off" the calories, assuming that all the food energy goes into increasing gravitational potential energy? (b) if, as is typical, only 20% of the food calories go into mechani- cal energy, what would be the answer to part (a)? (note: in this and all other problems, we are assuming that 100% of the food calories that are eaten are absorbed and used by the body. this is actually not true. aperson's "metabolic efficiency" is the percentage of calories eatenthat are actually used; the rest are eliminated by the body. metabolic efficiency varies considerably from person toperson.)