We start with a typical, FE$-$exam style problem. For the symmetric $($about the horizontal$)$ hollow box section below, find the maximum bending stress for the simply$-$supported beam shown below. The distributed load has a value of $q=-2k\frac{N}{m}$ and the beam span length is $4$ meters. The hollow box has outer rectangle dimensions of $10cm20cm.$ The hollow $($air$)$ dimensions are $8cm18cm.($Notes: You do not have to draw the shear and moment diagram. You can "remember" what the maximuim moment is since this is one of our $20$ basic diagrams. Use that. For the hollow section, it is symmetric. Hence the centroid is halfway up $($at $10cm)$ and you can use the "subtraction" method to get I.$)$ Answers: $I=27\mathrm{.}79{10}^{-6}{m}^4,$ the maximum stress in both tension and compression is $14\mathrm{.}4$MPa.