How to solve this problem and show steps of solving???

Given
Height of tower: 39.2
Acceleration due to gravity = 9.8 m/s² 

For the first stone:
initial velocity = u = 0 m/s

S = ut + 1/2 x a x t²
S = 4.9t²

For the second stone
initial velocity = u = 19.6 m/s

S = ut + 1/2 x a x t²
S = 19.6t - 4.9t²

19.6t - 4.9t² = 4.9t²
19.6t = 2 x 4.9t²
9.8 = 4.9t
t = 2

So S = 4.9t² = 4.9 * 4 = 19.6 m