Let O be the origin, and M and N be the points on the lines (x-5)/4=(y-4)/1=(z-5)/3 and (x+8)/12=(y+2)/5=(z+11)/9 respectively such that MN is the…

Let O be the origin, and M and N be the points on the lines $\displaystyle \frac{x-5}{4}=\frac{y-4}{1}=\frac{z-5}{3}$ and $\displaystyle \frac{x+8}{12}=\frac{y+2}{5}=\frac{z+11}{9}$ respectively such that MN is the shortest distance between the given lines. Then $\displaystyle \overrightarrow{O M} \cdot \overrightarrow{O N}$ is equal to $\displaystyle \_\_\_\_$.