A ring of radius R = 4 m made of a highly dense material has a mass m1=5.4×109kg distributed uniformly over its circumference. A highly dense particle of mass m2=6×108kg is placed on the axis of the ring at a distance 3 m from the center of the ring. Find the speed of the particle (in cm/s), when the particle is at the center of the ring. Except mutual gravitational interaction of the two, neglect all other forces.