$[6]$ A L shape beam with a rectangular cross section is loaded as shown. Answer the following questions:

$($a$)$ For cross section A$-$A$,$ what loading modes exist $($i$.$e$.,$ axial, transverse shear, bending and torsion$)?$ Calculate all non$-$zero internal forces$/$moments at the cross section.

$($b$)$ For cross section B$-$B$,$ what loading modes exist $($i$.$e$.,$ axial, transverse shear, bending and torsion$)?$ Calculate all non$-$zero internal forces$/$moments at the cross section.