7. The Earth's electric field creates a potential that increases 100 V for every meter of altitude. If an object of charge +4.5 mC and mass 68 g falls a distance of 1.0 m from rest under the influence of the Earth's electric and gravitational fields, what is its final kinetic energy? (A) 0.22 J (B) 0.45 J (C) 0.67 J (D) 1.1 J (E) 7.2 J