To find the gravitational force between the objects we use Newton's gravitaional law.
[tex]F=G\frac{m_1m_2}{r^2}[/tex]where G is the gravitational constant, m1 and m2 are the masses and r is the distance between the center of gravity of objects.
In this case, assuming the separation between the objects is at the border, the value of r is 20 m.
Then we have:
[tex]\begin{gathered} F=6.6743\times10^{-11}\cdot\frac{(8.5)(1.5)}{(20)^2} \\ =2.127\times10^{-12} \end{gathered}[/tex]Therefore the gravitational force between the objects is:
[tex]2.127\times10^{-12}\text{ N}[/tex]