Direction using Vectors: Derivation

Q. A stone is tied to a rope of length $2$ m and is whirled above his head horizontally by a man at a height of $9\text{m}$ from the ground. The stone covers a horizontal distance of $20\text{m}$ when the rope breaks. What is the magnitude of the centripetal acceleration when the stone was in the circular motion?

1. $111.11{\text{m/s}}^2$
2. $123.5{\text{m/s}}^2$
3. $99.25{\text{m/s}}^2$
4. $61.72{\text{m/s}}^2$