(22-28) A spherical rubber balloon carries a total charge Q uniformly distributed on its surface. At

(22-28) A spherical rubber balloon carries a total charge Q uniformly distributed on its surface. At t = 0 the nonconducting balloon has radius r_0 and the balloon is then slowly blown up so that r increases linearly to 2r_0 in a time T. Determine the electric field as a function of time (a) just outside the balloon surface and (b) at r=3.2r_0.