The angle of elevation of the top of a tower at a point on level ground is 45°. When moved 20 m towards the tower, the angle of elevation becomes 60°. What is the height of the tower?
1
\(10\,(\sqrt 3 \, - \,1)\) m
2
\(10\,(\sqrt 3 \, + \,1)\) m
3
\(10\,(3 - \sqrt 3)\) m
4
\(10\,(3 + \sqrt 3)\) m