One particle has a mass of 4.00 x 10-3 kilogram and a charge of +7 µC. A second particle has a mass of 7.00 x 10-3 kilogram and the same charge. The two particles are initially held in place and then released. The particles fly apart, and when the separation between them is 0.104 meter, the speed of the 4.00 x 10-3 kilogram particle is 119 m/s. Computer the initial separation between the particles.