Answer
$q = 5.72\times 10^{13}~C$
Work Step by Step
We can equate the magnitude of the gravitational force and the electrostatic force to find the required positive charge $q$:
$\frac{q^2}{4\pi~\epsilon_0~r^2} = \frac{G~M~m}{r^2}$
$q^2 = 4\pi~\epsilon_0~G~M~m$
$q = \sqrt{4\pi~\epsilon_0~G~M~m}$
$q = \sqrt{(4\pi)~(8.854\times 10^{-12}~F/m)~(6.67\times 10^{-11}~N~m^2/kg^2)~(5.98\times 10^{24}~kg)(7.36\times 10^{22}~kg)}$
$q = 5.72\times 10^{13}~C$
