A toroid having a cross section of rectangular shape is defined by the following surfaces: the cylinders $\rho=2$ and $\rho=3 \mathrm{~cm}$, and the planes $z=1$ and $z=2.5 \mathrm{~cm}$. The toroid carries a surface current density of $-50 \mathbf{a}_{z} \mathrm{~A} / \mathrm{m}$ on the surface $\rho=3 \mathrm{~cm}$. Find $\mathbf{H}$ at the point $P(\rho, \phi, z):(a) P_{A}(1.5 \mathrm{~cm}, 0$, $2 \mathrm{~cm}) ;\left(\right.$ b) $P_{B}(2.1 \mathrm{~cm}, 0,2 \mathrm{~cm}) ;$ (c) $P_{C}(2.7 \mathrm{~cm}, \pi / 2,2 \mathrm{~cm}) ;$ (d) $P_{D}(3.5 \mathrm{~cm},$,
$\pi / 2,2 \mathrm{~cm})$