Answer
$U = -4.4\times 10^{-11}~J$
Work Step by Step
In Problem 3, we found that the distance between the particles is $~~d = 19~m$
We can find the gravitational potential energy of the two-particle system:
$U = -\frac{G~M_1~M_2}{d}$
$U = -\frac{(6.67\times 10^{-11}~N~m^2/kg^2)(5.2~kg)(2.4~kg)}{19~m}$
$U = -4.4\times 10^{-11}~J$
