A straight highway leads to the foot of the tower. A man standing at the top of the tower observes a car at an angle of depression of
30∘30∘, which is approaching the foot of the tower with a uniform speed.
9 minutes9 minutes later, the angle of depression of the car is found to be
60∘60∘. What is the time taken by the car after
9 minutes9 minutes to reach the foot of the tower?