A balloon is moving along with constant upward acceleration of I $\mathrm{m}/{\mathrm{s}}^2$. A stone is thrown from the balloon downwards with speed 10 m/s with respect to the balloon. At the time of projection balloon is at height 120 m from the ground and is moving with speed 20 m/s. Find the time required to fall on the ground by the stone after the projection.

• A

  6 s

• B

  4 s

• C

  3 s

• D

  4.5 s