
Solution is in attachment ~
I hope that you got what you were looking for, and if there's different data then go through the same procedure, using same formula with different values and you will get your answer ~

Answer:
1.73 seconds
Explanation:
The velocity the ball first hits the ground with is:
v² = v₀² + 2aΔx
v² = (0 m/s)² + 2 (-10 m/s²) (-20 m)
v = -20 m/s
The velocity it rebounds with is 3/4 of that in the opposite direction, or 15 m/s.
The time it takes to return to the ground is:
Δx = v₀ t + ½ at²
0 = (15 m/s) t + ½ (-10 m/s²) t²
0 = t (15 − 5t²)
t = √3
t ≈ 1.73 seconds
Explanation:
It is known that the relation between work and force is as follows.
w = 
where,
= angle between the applied force and direction of movement of the object which is zero in this case. As, cos (0) = 1.
Therefore, d = 
(i) For w = 36 J, and F = 9 N then value of d will be as follows.
d = 
= 
= 4 m
(ii) For w = 36 J, and F = 12 N then value of d will be as follows.
d = 
= 
= 3 m
(iii) For w = 36 J, and F = 6 N then value of d will be as follows.
d = 
= 
= 6 m
(iv) For w = 36 J, and F = 18 N then value of d will be as follows.
d = 
= 
= 2 m
Well the sea level would be 120 ml lower but to this day the sun is hotter than before research shows that the ice would melt a little faster than the ice age but it is only a prediction but that would be the result