Alexander wants to know exactly how many bars to pack in his backpack for the journey. to provide a margin of safety, he assumes that he will need as much energy for the return trip as for the uphill climb. how many bars should alexander pack?

Thank you for posting your question here at . To answer the above question, 

First calculate the Joules (work done by Alexander), divide by 4.184 to get calories and then divide by 1000 to get kilocalories or Calories. 

201 lbs will be 90 kgs approx. And work done will be mgh = 90 x 10 x 5220 kg.m Double that for coming down.

We need more info then that