The graph of mass versus kinetic energy shows that mass is proportional to kinetic

  #_total = 4.38 10⁹ liter

Explanation:

For this exercise we can use a direct proportion rule (rule of three). If 4 people use 1200 liters how much water 1 person consumes

            #_water = 1 person (1200 liter / 4 person)

            #water = 300 liters

Now we look for the consumption of this person in a year, if 1 person consumes 300 liters 1 day, how many liters they consume in a year (365 days)

           #_water_person_total = 365 days (300 liters / 1 day)

           #_water_person_total = 109500 liters

This is the water consumption of 1 person in a year, the total of 40000 people how much they consume

           #_total = 40000 person (109500 liter / 1 person)

           #_total = 4.38 10⁹ liter