A positive charge of 625 nC is uniformly distributed around a circular ring of radius 3 m that is positioned in the x-y plane. The center of the circle is at the origin. The relative permittivity of the medium is Epsilon_r = 1. Find the electric field at the point (0, 0, 4m). Also find the force on a particle carrying positive charge of 75 µC located at (0, 0, 4m).