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The answer you are looking for is B, hope this helps.
Answer:
4 m/s
Explanation:
KE=1/2mv^2
720=1/2(90)
720=45v^2
divide by 45
16= v^2
over the square root
4=v
v= 4m/s
As the rocket is launched from the ground its height will go on increasing till it stops
So the height of rocket will be maximum when its speed becomes zero
so here we can use energy conservation theory




So it will reach upto height 7.35 m