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Physics Work,Power & Energy Level: High School

Assuming an efficiency of 25% for the muscle system in the process of converting food energy into mechanical work , how much energy would be used by a person of mass 75 kg . (weight 165 lb.) in the process of climbing four flights of stairs for a total height of 15 meters ? Find the answer in joules and convert to dietary calories (1 dietary calorie = 4186 joules)