Thread: urgent... gravitational potential between two spheres.

two spheres their masses are :m1=m2=1.2x10^-8 kg are placed 10 cm away from each other. (r=10 cm) How is the gravitation potential ( V=?)in the point A which is situated 6 cm away from the first sphere and of course 4 cm away from the second one.

The result is given and is -2.33 x 10^17J/kg but I can't find how ?
It has to be with this formula: V=kq/r^2

Any help is appreciated!
Thanks...