The amplitude of wave disturbance propagating in the positive $x$-direction is given by $y = \frac { 1 } { ( 1 + x ) ^ { 2 } }$ at time $t = 0$ and $y = \frac { 1 } { 1 + ( x - 2 ) ^ { 2 } }$ at $t = 1 s$, where $x$ and $y$ are in metres. The shape of wave does not change during the propagation. The velocity of the wave will be $\mathrm { m } \mathrm { s } ^ { - 1 }$.