A boy whirls a stone in a horizontal circle of radius 1.2 m and at height 2.0 m above ground level. The string breaks, and the stone flies horizontally and strikes the ground after traveling a horizontal distance of 10 m. What is the magnitude of the centripetal acceleration of the stone while in circular motion in m/s^2?

im stumped :\

when it's asking for magnitude... am i looking for:
-the distance it broke off to the point it landed? .. 10m

or

1.2m + 10m?

how do i determine the velocity?! help!

determine the time it takes for the stone to fall 2 meters. Then velocty= 10m/time