Determine maximum bending stresses

Constructing the moment diagram

Considering the segment
from x = 1.5 m to x = 1.5 m

     area under
                shear =  0.00 kN-m
     concentrated
           moments =  +20.00 kN-m
     total bending
            moment =  +20.00 kN-m

       at x = 1.5 m,    M =    -3.00 kN-m
           total bending
               moment   =   +20.00 kN-m
       at x = 1.5 m,   M =   +17.00 kN-m