(d) $h = \frac{1}{2}gt^{2}\ \Rightarrow t = \sqrt{\frac{2 \times 1960}{9.8}} = 20\ s$
$\therefore\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ s = AB = ut = 600 \times \frac{20}{60 \times 60}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = 3.33\ km$