Explanation:

- The stone is thrown vertically upward with an initial velocity \( u \).

- Tower height is given as \( 12u^2 \).

- We need to determine the final velocity \( v \) when the stone hits the ground.

- Utilize the equation of motion: \( v^2 = u^2 + 2gh \).

- Here, \( g \) is the acceleration due to gravity and \( h \) is the height the stone falls.

- Plug \( h = -12u^2 \) and \( g = 9.8 \, \text{m/s}^2 \) (approximate for simplicity).

- Solve: \( v^2 = u^2 + 2(-9.8)(-12u^2) \).

- Simplifying, \( v^2 = u^2 + 24u^2 = 25u^2 \).

- Therefore, \( v = 5u \).

Correct Answer: Option:3 - 5U