A simply supported beam AB (span 4 m) with supports at the ends A and B, is subjected to a uniformly distributed load of 4 kN/m through the span AB. Determine the maximum bending stress developed in the beam cross-section. The cross-section of the beam is rectangular with a width of 120 mm and a depth of 200 mm, and the beam is placed with a depth of 200 mm in the vertical direction. Assume E as the modulus of elasticity of the material of the beam.