From shear-force and bending-moment diagrams, we find that the shear force at B is V = +5 kN.
The shear stress in the beam will be computed with the transverse shear stress formula:
where V = internal shear force,
Q = moment of area about the neutral axis,
I = moment of inertia about the centroidal axis, and
t = width of the beam at the point of interest.