Your answer is partially correct.
A circular plastic disk with radius R = 1.67 cm has a uniformly distributed charge Q = +(3.90 x10$^6$)e on one face. A circular ring of width
38.4 µm is centered on that face, with the center of that width at radius r = 0.715 cm. In coulombs, what charge is contained within the
width of the ring?
