${}_c=k\frac{{}^{2}E}{12(1-v^2)(\frac{b}{t}{)}^2}$

Someone has mandated a restriction on the slenderness ratio $(\frac{b}{t})$ of a steel flange, limiting it to $85\%$ of the value where full yield and elastic plate buckling coincide, and with a plate$-$buckling coefficient of $0\mathrm{.}8,$ we need to express this limit in a traditional form without solving for it