Solving a problem in physics section 71 point 26 electr

26. A droplet of oil is resting in the electric field of a flat capacitor with horizontally located plates, the charge of which is equal to the elementary charge (Fig.). The voltage U = 500 V was applied to the plates, the distance between the plates was d = 0.5 cm. Find the droplet radius R. Oil density ρ = 900 kg / m3, medium - air.