4. A spherically symmetric charge distribution has the following volume charge density p: p(7) = er/R T R where y is a constant. a) What are the units of the constant y? b) What is the total charge Q contained in the distribution? c) Using Gauss's law find the electric field in the regions r R. d) Now suppose this distribution is enclosed within a concentric spherical conducting shell with inner radius 2R and outer radius 3R such that the total electric field for the region r > 3R is zero. What is the net charge of this conducting shell and what is the charge density on its inner and outer surfaces (at r = 2R and r = 3R)