Consider two spheres that are separated by a distance of 3.5 cm and are held in place on a frictionless track.The first sphere has a charge of 3.5 x 10^-6 C and a mass of 1.5 kg. The second sphere has a charge of 4.2 x 10^-6 C and a mass of 1.2 kg. Calculate the electrostatic potential energy of the system