let its velocity  was v when it was in circular motion...after the string breaks , stone will move parabolically...

H = 2.7 (above the ground)

U_x= v       (velocity in circular path)

a_y = -g

for horizontal motion threre is no accleration so a_x =0

for verticle motion ,

S = gt²/2

2.7 = gt²/2

t = 0.74sec

now for horizontal motion

speed = distance/time

 U_x = 10/(0.74)                                   (distance 10m (given))

U_x = 13.51m/s

with this velocity particle was circulating .....

a_c(centripital accleration) = v²/r = (13.51)²/1.5 = 122 m/s²

Approved