A charged cloud system produces an electric field in the air near Earth's surface. A particle of charge -1.6 x 10- C is acted on by a downward electrostatic force of 3.5 x 10- N when placed in this field. (a) What is the magnitude of the electric field? (b) What is the magnitude of the electrostatic force on a proton placed in this field? (c) What is the gravitational force on the proton? (d) What is the ratio of the electrostatic force to the gravitational force in this case