A bird is perched on the top of a tree 20 mts high and its elevation from the point on the ground is $45°$ . It flies off horizontally straight away from the observer and in one second the elevation of the bird is reduced to  $30°$. Then Two times of speed of bird is $\lambda$ $m/s$ then $\left[\lambda \right]$ is________  (where $\left[.\right]$ represents G.I.F)