Assuming that the prismatic beam $\backslash ($ A B $\backslash )$ has a rectangular cross section, derive an expression for the maximum strain energy density in terms of the strain energy $\backslash ($ U $\backslash )$ and the volume of the beam $\backslash ($ V $\backslash ).($Round the final answer to three decimal places.$)$

The maximum strain energy in the beam is $\backslash (\backslash$frac$\{$U$\}\{$V$\}\backslash ).$