Write down the two Maxwell equations that govern steady magnetic fields. Show that the boundary conditions satisfied by the magnetic field on either side of a sheet carrying a surface current of density $\mathbf{s}$, with normal $\mathbf{n}$ to the sheet, are

$$\mathbf{n} \times \mathbf{B}_{+}-\mathbf{n} \times \mathbf{B}_{-}=\mu_{0} \mathbf{s}$$

Write down the force per unit area on the surface current.