Two trains $$A$$ and $$B$$ of length $$l$$ and $$4l$$ are travelling into a tunnel of length $$L$$ in parallel tracks from opposite directions with velocities $$108$$ km h$$^{-1}$$ and $$72$$ km h$$^{-1}$$, respectively. If train $$A$$ take $$35$$ s less time than train $$B$$ to cross the tunnel then, length $$L$$ of tunnel is:
(Given $$L = 60 \ l$$)










