Acceleration of the particle is 'g'.
Apply second equation of the motion we have
9h/25 = (1/2)gt^2
And the total time taken by it to come down is √(2h/g)
So, t=(3/5)*(total time taken by particle to come down)
Total time taken by it is 5t/3
So, applying second equation of motion again
So, the answer is 25gt^2/18
Tell me if there is any doubt I will post written solution.