Answer :
As we know that here no air resistance while ball is moving in air
So here we will say that
initial total energy = final total energy
[tex]KE_i + U_i = KE_f + U_f[/tex]
here we know that
[tex]Ui = U_f = 0[/tex] (as it will be on ground at initial and final position)
so we will say
[tex]KE_i = KE_f[/tex]
since mass is always conserved
so we will say that final speed of the ball must be equal to the initial speed of the ball
so we have
[tex]v_f = v_i = 30 m/s[/tex]