\f(a) (5 points) Consider the auxiliary field H(r). Explain why in this problem it is possible to introduce a single scalar potential function W(r) which satisfies H = -V W. (b) (5 points) Write down the equation W satisfies in each of the three regions: r b. (c) (10 points) At each of the two surfaces, r = a and r = b, write down a set of two appropriate boundary conditions, one for the value of W itself, and another for its normal derivative