Problem 1.4 (Not assigned. For practice only.) Consider a spherically-symmetric volume charge distribution p(r) = poe=1*', where py and a are constants. Review Example 1.6. To do the integral, you can make the substitution u = (r/a)>. a) Find the total amount of charge @i, (b) contained within a sphere of radius b centered on the origin. b) In this week's notes, I quoted, but did not derive, a simple form for the electric field of spherically- symmetric charge distributions. Use the result from part a to find the magnitude and the direction of the electric field at any point in space. Problem 1.5 (Not assigned. For practice only.) A uniformly-charged thin ring of radius @ and net charge Q > 0 lies in the zy-plane, centered at the origin, as shown above. Find the magnitude and direction of the electric field at all points on the positive z-axis