A ring of charge of radius ro lies in the xy plane with its center at the origin. The charge counterclockwise from = 0 to = 180 is uniformly distributed with the total charge equaling Q. The charge counterclockwise from = 180 to = 360 is uniformly distributed with the total charge for this half of the ring equaling Q. What is the direction of the electric field on the z-axis at the position (x, y, z) = ( 0, 0, ro )