A charged cloud system produces an electric field in the air near the Earth's surface. A particle of charge -2.5 10-9 C is acted on by a downward electrostatic force of 3.0 10-6 N when placed in this field. (a) What is the magnitude of the electric field? N/C (b) What are the magnitude and direction of the electrostatic force Fel exerted on a proton placed in this field? N (c) What is the magnitude of the gravitational force Fg on the proton? N (d) What is the ratio Fel / Fg in this case?