The ratio of Coulomb's electrostatic force to the gravitational force between an electron and a proton separated by some distance is 2.4 $\times$ 10³⁹. The ratio of the proportionality constant, $K = {1 \over {4\pi {\varepsilon _0}}}$ to the gravitational constant G is nearly (Given that the charge of the proton and electron each = 1.6 $\times$ 10^$-$19 C, the mass of the electron = 9.11 $\times$ 10^$-$31 kg, the mass of the proton = 1.67 $\times$ 10^$-$27 kg) :