You plan to throw stones by using a sling of length 1.8 m which you whirl over your head. Suppose you wish to throw a stone a distance of 22 m. What must be the centripetal acceleration of the stone just before its release if it is to reach this distance? Assume that the release height is 2.8 m.
I thought that the person's probably slinging it horizontally. So the initial velocity at y is 0. From that I found the time it took and then the horizontal velocity. I thought that would also be the sling's speed so I converted it into radians, found the centripetal speed and got 470.6 rad/s/s and since they didnt understand my units converted it into m/s/s and got 837.95 m/s/s....and then got it wrong. bleh i know it might be confusing but can someone tell me where I went wrong?

EDIT: NEVERMIND i was using the wrong units haha i was right. it's 470.6 m/s/s

Question

You plan to throw stones by using a sling of length 1.8 m which you whirl over your head. Suppose you wish to throw a stone a distance of 22 m. What must be the centripetal acceleration of the stone just before its release if it is to reach this distance? Assume that the release height is 2.8 m. 
I thought that the person's probably slinging it horizontally. So the initial velocity at y is 0. From that I found the time it took and then the horizontal velocity. I thought that would also be the sling's speed so I converted it into radians, found the centripetal speed and got 470.6 rad/s/s and since they didnt understand my units converted it into m/s/s and got 837.95 m/s/s....and then got it wrong. bleh i know it might be confusing but can someone tell me where I went wrong?

EDIT: NEVERMIND i was using the wrong units haha i was right. it's 470.6 m/s/s