1. The problem statement, all variables and given/known data The nominal food-energy value of 1.00g of butter is about 7.20 food calories. If all this energy could be converted completely to mechanical energy, how much butter would be required to power a 65.0kg mountaineer on her journey from Lupine Meadows (elevation 2070m) to the summit of Grand Teton (4196m)? 2. Relevant equations Mass*Gravity*Height 3. The attempt at a solution What I tried was (65 * 9.81 * 2126) to find the Joules of energy required for the journey. Then converted 7.2 food calories to 30.1248J and divided to find the grams. I came out with approx 4.5x10^4g of butter, however it is not being accepted as correct. What am i doing wrong?