3) A thin circular plate has its axis as the z-axis, and its center is the origin of our coordinate system. It has radius R, and charge 2Q. Two thin rings, each of charge -Q, and also radius R, are located along the same axis each a distance R (same value) on either side of the disk. It would look sort of like this: 000 a) What is the value of the electric field at points along the mutual axis at values => R? (So, on the right side only.) b) What is the value of the electric potential at points along the mutual axis at values z > R?