#### Answer

1.48m

#### Work Step by Step

Let height above top of the window=h.
$S=ut+\frac{1}{2}at^{2}=0+\frac{1}{2}gt^{2}$
Therefore, $S=4.9t^{2}$
$S_{1}=4.9t_{1}^{2}$
$S_{2}=4.9t_{2}^{2}$
So, $S_{1}-S_{2}=4.9 \times (t_{1}-t_{2})(t_{1}+t_{2})$
i.e. $1.35=4.9\times 0.21\times (t_{1}+t_{2})$
$(t_{1}+t_{2})=1.31s$
Therefore, $t_{1}=0.76s$ and $t_{2}=0.55s$
So, $S_{2}=4.9t_{2}^{2}=4.9\times 0.55^{2}=1.48m$