It has been experimentally observed that the electric field in a large region of earth's atmosphere is directed vertically down. At an altitude of 300 m, the electric field `60 Vm^(-1)`. At an altitude of 200 m, the field is 100 V m^(-1), the field is `100 Vm^(-1)`. Calculate the net amount of charge contained in the cube of 100 m edge, located between 200 and 300 m altitude.