F = k (q1*q2) / r^2
k=9*10^9
F = 9*10^9 (-2*10^-8*-9*10^-8) / 9^2 = (9*10^9 * 18*10^-8) / 81 = 1620/81 = 20 H
F = k (q1*q2) / r^2
k=9*10^9
F = 9*10^9 (-2*10^-8*-9*10^-8) / 9^2 = (9*10^9 * 18*10^-8) / 81 = 1620/81 = 20 H