So over here, you are using 5,400 Calories a day, it you are working 10 hours per day and it requires 400 working hours, you are going to be working 40 days, right, 400 divided by 10, 40 days times 5,400 Calories per day, it is going to take a human, just the human part, not even thinking about the 6,000 Calories necessary to maintain and make that plough, the human is going to expend 216,000 Calories to till, to plough that 1 hectare of land. 