how is this effective length $0\mathrm{.}084$ found using these equations??$($a$).I_5=3000\frac{(200{)}^3}{12}=2\mathrm{.}0{10}^{9}m{m}^4$

$I_c=300\frac{(300{)}^3}{12}=6\mathrm{.}75{10}^{8}m{m}^4$

$k_{\text{t}\text{o}\text{p}}=k_{\text{b}\text{o}\text{t}\text{t}\text{o}\text{m}}={\displaystyle \underset{?}{\overset{?}{}}}\frac{\frac{I_c}{l}}{2}{\displaystyle \underset{?}{\overset{?}{}}}(\frac{I_b}{l})=0\mathrm{.}084>0\mathrm{.}1$