What is the radius of gyration of the given figure?
1
\(\frac{{B{D^3}}}{{12}} - \frac{{b{d^3}}}{{12}}\)
2
\(\frac{{B{D^3} - b{d^3}}}{{12\left( {BD - bd} \right)}}\)
3
\(\sqrt {\frac{{B{D^3} - b{d^3}}}{{12\left( {BD - bd} \right)}}}\)
4
\(\sqrt {\frac{{B{D^3} - b{d^3}}}{{3\;BD}}}\)