From a tower 18 m high the angle of elevation of the top of a tall building is 45° and the angle of depression of the bottom of the same building is 60°. What is the height of the building in meters

• A. \(12 + 6\sqrt 3\)
• B. \(6\left( {3 + \sqrt 3 } \right)\)
• C. \(18 + \sqrt 2\)
• D. \(6\left( {3 + \frac{{\sqrt 3 }}{2}} \right)\)