At a distance of 0.75 meters from its center, a Van der Graaff generator interacts as if it were a point charge, with that charge concentrated at its center. A test charge at that distance experiences an electric field of 4.5 × 10^5 newtons/coulomb. What is the magnitude of charge on this Van der Graaff generator?

a. 1.7 × 10^(-5) coulombs
b. 2.8 × 10^(-5) coulombs
c. 3.0 × 10^(-5) coulombs
d. 8.5 × 10^(-5) coulombs