Answer 41.7 years old
I answer this question already and it was correct!
Answer:

Explanation:
Torque is defined as the cross product between the position vector ( the lever arm vector connecting the origin to the point of force application) and the force vector.

Due to the definition of cross product, the magnitude of the torque is given by:

Where
is the angle between the force and lever arm vectors. So, the length of the lever arm (r) is minimun when
is equal to one, solving for r:

The momentum of ball is given by:
Since both have the same momentum, we have:
Number 3If you notice any mistake in my english, please let me know, because i am not native.