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 \( 108 \, \text{km/h} \) and \( 72 \, \text{km/h} \), respectively. If train' \( A \)' take \( 35 \, \text{s} \) less time than train '\( B \)' to cross the tunnel then, length '\( L \)' of tunnel is: (Given \( L = 60 \, l \))
