Question $55$ :

A civil engineer is designing a reinforced concrete beam to span a distance of $4$ meters and support a uniformly distributed load of $20$ kilonewtons per meter $($kN$/$m$).$ Calculate the maximum bending moment $($M$)$ acting on the beam and determine the required section modulus $($S$)$ to ensure structural stability, assuming a concrete compressive strength of $30$ megapascals $($MPa$).$