Bending stress in a beam with overhang

Constructing the shear diagram

Considering the segment
from x = 4 m to x = 4 m

 area under shear
     diagram =     0.00 kN-m
 concentrated
   moments =   -40.00 kN-m
 change in bending
     moment = -40.00 kN-m

    at x = 4 m,     M =   +23.20 kN-m
 change in bending
          moment    =   -40.00 kN-m
    at x = 4 m,     M =   -16.80 kN-m