Coulomb's law compared with gravitation

2017 1 question

1. Suppose the charge of a proton and an electron differ slightly. One of them is –e, the other is $(e + \Delta e)$. If the net of electrostatic force and gravitational force between two hydrogen atoms placed at a distance d (much greater than atomic size) apart is zero, then $\Delta e$ is of the order of [Given mass of hydrogen $m_h = 1.67 \times 10^{-27}$ kg]