On the top of a tower there is a flag staff. At a point 200m from the foot of the tower, the angles of elevation of the top and bottom of the flag staff are respectively $$60^{\circ}$$ and $$45^{\circ}$$. Then the length of the flag staff (mts) is

A

$$200\sqrt{3}$$

B

$$200(\sqrt{3} - 1)$$

C

$$100\sqrt{3}$$

D

$$200(\sqrt{3} + 1)$$