Column AB has a uniform cross section with b $=12$ mm and d $=22$ mm$.$ The

column is braced in the xz plane at its midpoint C and a carries a centric load P of

magnitude $3\mathrm{.}8$ kN$.$ Knowing that a factor of safety of $3\mathrm{.}2$ is required, determine the

largest allowable length L$.$ Use E $=200$ GPa.