JEE Main 25 Feb 2021 Shift 1 Solved Paper

A man is observing, from the top of a tower, a boat speeding towards the tower from a certain point A, with uniform speed. At that point, angle of depression of the boat with the man's eye is 30∘ (ignore man's height).
After sailing for 20s, towards the base of the tower (which is at the level of water), the boat has reached a point B, where the angle of depression is 45∘. Then, the time taken (in seconds) by the boat from B to reach the base of the tower is