Centre of the circle =(23,1) Equation of diameter =2x+3y−k=0 $\begin{aligned}
& 2\left(\frac{3}{2}\right)+3(1)-\mathrm{k}=0 \
& \Rightarrow \mathrm{k}=6
\end{aligned}Now,Equationofellipsebecomes\begin{aligned}
& x^2+9 y^2=36 \
& \frac{x^2}{6^2}+\frac{y^2}{2^2}=1
\end{aligned}\begin{aligned} & \text { length of } L R=\frac{2 b^2}{a}=\frac{2.2^2}{6}=\frac{8}{6}=\frac{4}{3}=\frac{m}{n} \ & \therefore 2 m+n=2(4)+3=11\end{aligned}$