Given:- Velocity of stone projected upwards = 20 m/s

Time taken by stone to reach ground = 8 sec
To find:- The height of tower.

Let the height of tones be him.

Then, the particle after projection will reach a maximum height at which its final velocity mill be zeno.

By 3^rd eqⁿ of mation

${\mathrm{v}}_{\mathrm{f}}^2={\mathrm{v}}_{\mathrm{i}}^2+2\mathrm{as}$

$0=(20{)}^2+2(-10)\mathrm{s}$

$\mathrm{s}=\frac{400}{20}$

s = 20 m

Now, the total time is given t = 8 sec for the whole journey ide. (ABC)
Time taken to reach B from A is :
v = u + at
0 = 20 + (–10)t

$\boxed{\mathrm{t}=2\sec }$

Now, find the distance, BC travelled in time t_BC= 6 sec.

$\mathrm{s}=\mathrm{ut}+\frac{1}{2}{\mathrm{at}}^2$

$\mathrm{s}=0\times 6+\frac{1}{2}\times 10\times 6^2$

$\mathrm{s}=\frac{36\times 10}{2}$

$\boxed{\mathrm{s}=180 \mathrm{m}}$

Distance BC = h + 20, substilute BC=180 m

180 = h + 20

$\boxed{\mathrm{h}=160 \mathrm{m}}$

us, the height of the tower is 160 m.