Answer:
I was going to give you the paper where I saw it but since you are not giving enough points I can not give you so I am only going to give you some of these that are here sorry
Explanation:
1.

x=5

7.
5,12,13
9.

You can calculate potential energy by:
U = m.g.h
Where, U = potential energy
m = mass
g = acceleration due to gravity
h = height
Hope this helps!
it cannot be reuse and replaced for long period of time.hope it helps u
The answer is 5. To find the advantage you just divide 20 by 4.