In the over$-$hanged beam which has a box shaped cross section:

$20$dots$40$:$\mathrm{.}20.$

$($a$)$ Find the shear stress $({}_E)$ and normal stress $({}_E)$ acting at point E

$($b$)$ Find the maximum shear stress $({}_{\text{m}\text{a}\text{x}})$ and maximum normal stress $({}_{\text{m}\text{a}\text{x}})$

in the beam.