The angular depressions of the top and the foot of a tower, as seen...

The angular depressions of the top and the foot of a tower, as seen from the top of a second tower which is $150$ meters high and standing on the same level as the first, are $ta{n}^{- 1}\dfrac{4}{3}$ and $ta{n}^{- 1}\dfrac{5}{2}$ respectively. If the distance between their tops is $d$, then $\dfrac{d}{20}$ is