The cantilevered bar is subjected to two constant loads. Force $P=20lbf,F=10lbf$ acts at point A and is in the $+x$ direction. Force $F$ acts at point $B$ and is in the $+y$ direction.

The bar is a solid rod with a constant $1/2-$in diameter.

Determine the following.

$($a$)$ The critical element$($s$)$ of the bar.

$($b$)$ Show the state of stress on a stress element for each critical element.

I would like something very clear with illustration