Food calories needed to climb stairs 6 m at 10% efficiency

[shuman0101]

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)

 

[SteamKing]

A food calorie is a Kcal. (You can look it up.)