JEE Math Practice Question

The angle of elevation of the top of a vertical tower standing on a horizontal plane is observed to be 45o from a point A on the plane. Let B be the point 30 m vertically above the point A. If the angle of elevation of the top of the tower from B be 30o, then the distance (in m) of the foot of the tower from the point A is :

1. A.$$15\left( {1 + \sqrt 3 } \right)$$
2. B.$$15\left( {3 - \sqrt 3 } \right)$$
3. C.$$15\left( {3 + \sqrt 3 } \right)$$
4. D.$$15\left( {5 - \sqrt 3 } \right)$$