A charged oil drop that has a mass of \(5.00 \times 10^{-12} \mathrm{~kg}\) and carries 10 elementary charges is centered \(50 \mathrm{~mm}\) below the center of an oppositely charged nonconducting sphere that has a radius of \(5.0 \mathrm{~mm}\). What uniformly distributed charge should the sphere be given so that the electric force it exerts on the drop causes the drop to float in the air for an instant? Treat the drop as a particle.