Develop the potential formulation for electrodynamics with magnetic charge (Eq. 7.44). [Hint: You'll need two scalar potentials and two vector potentials. Use the Lorenz gauge. Find the retarded potentials (generalizing Eqs. 10.26), and give the formulas for E and B in terms of the potentials (generalizing Eqs. 10.2 and 10.3).]