There are two bottles of 10 liter; each completely filled with water. Now 2 persons having empty bottles of 4 liter and 5 liter want to take 2-2 liters of water. You can use only these 4 bottles (10 liter-full, 10 liter-full, 5 liter-empty, 4 liter-empty) to transfer the water. Wasting or throwing of water is not permitted. How can this be done?
Note: It is assumed that you can not measure water level by comparing water level, or by judging, it should be exact 2 liters of water finally in each 4 and 5 liter water bottle.