Train A and train B are running on parallel tracks in opposite directions with speeds of $36$ km hour$^{-1}$ and $72$ km hour$^{-1}$, respectively. A person is walking in train A in the direction opposite to its motion with a speed of $1.8$ km hour$^{-1}$. Speed (in m s$^{-1}$) of this person as observed from train B will be close to: (take the distance between the tracks as negligible)