A man is walking towards a vertical pillar in a straight path, at a uniform speed. At a certain point A on the path, he observes that the angle of…

A man is walking towards a vertical pillar in a straight path, at a uniform speed. At a certain point $\displaystyle A$ on the path, he observes that the angle of elevation of the top of the pillar is $\displaystyle 30$°. After walking for $\displaystyle 10$ minutes from $\displaystyle A$ in the same direction, at a point $\displaystyle B$, he observes that the angle of elevation of the top of the pillar is $\displaystyle 60$°. Then the time taken (in minutes) by him, from $\displaystyle B$ to reach the pillar, is :