As we know that electrostatic force between two charges is given as
[tex]F = \frac{kq_1q_2}{r^2}[/tex]
here we know that electrostatic repulsion force is balanced by the gravitational force between them
so here force of attraction due to gravitation is given as
[tex]F_g = 1.98 \times 10^{20} N[/tex]
here we can assume that both will have equal charge of magnitude "q"
now we have
[tex]1.98 \times 10^{20} = \frac{kq^2}{r^2}[/tex]
[tex]1.98 \times 10^{20} = \frac{(9\times 10^9)(q^2)}{(3.84 \times 10^8)^2}[/tex]
[tex]1.98 \times 10^{20} = (6.10 \times 10^{-8}) q^2[/tex]
now we have
[tex]q = 5.7 \times 10^{13} C[/tex]
