Answer
$v = \sqrt{\frac{Gm}{R_i}}$
Work Step by Step
In part (b), we found that the kinetic energy of each body is $~~\frac{Gm^2}{2R_i}$
We can find the speed of each body relative to us:
$K = \frac{1}{2}mv^2 = \frac{Gm^2}{2R_i}$
$v^2 = \frac{Gm}{R_i}$
$v = \sqrt{\frac{Gm}{R_i}}$
