Need help with a problem involving work and calories

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To calculate the food calories needed for a 70 kg person to run up 6 m of stairs with 10% efficiency, the potential energy (P.E.) is determined using the formula P.E. = mgh, resulting in approximately 4116 J. Converting this energy into calories yields about 9830 calories. However, the answer key indicates that the correct value is 9.9 calories, which refers to kilocalories (Kcal), commonly known as food calories. The confusion arises from the distinction between calories and kilocalories. Understanding this difference is crucial for accurate energy consumption calculations.
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Homework Statement


A person whose mass is 70 kg runs up a flight of stairs through a vertical height of 6 m. If she uses her food with an efficiency of 10%, how many food calories does she have to consume to do this work?

Homework Equations



P.E=mgh=W

(Output/input)*100 = Efficiency

The Attempt at a Solution



I assumed that mgh=w because there is not kinetic energy at the top, so I just solved for mgh and got 4116J. I converted that into calories and found the input using the formula above, an I got ~9830 cals. When I looked at the answer key it said 9.9 cals( not Kcals)
 
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A food calorie is a Kcal. (You can look it up.)
 

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