$7\mathrm{.}3-13$ A shear wall in a reinforced concrete building is subjected to a vertical uniform load of intensity $q$ and a horizontal force $H,$ as shown in the first part of the figure. $($The force $H$ represents the effects of wind and earthquake loads.$)$ As a consequence of these loads, the stresses at point $A$ on the surface of the wall have the values shown in the second part of the figure $($compressive stress equal to $1100$ psi and shear stress equal to $480$ psi$).$

$($a$)$ Determine the principal stresses and show them on a sketch of a properly oriented element.

$($b$)$ Determine the maximum shear stresses and associated normal stresses and show them on a sketch of a properly oriented element.