$[25$p$]$ A horizontal steel pipe $AB$ is mounted to a wall, see Fig. It has an arm $BC$ attached

to end B$,$ see Fig. below

Determine:

a$)$ Bending and shear stresses $({}_x$ and ${}_{xy})$ at point $D,$ located on top of the pipe, $15$ cm

from end B$.$

b$)$ Principal stresses at point D

c$)$ Max shear stress at point D

PIPE AB$-$CROSSSECTION