A vertical pole fixed to the ground is divided in the ratio 1 : 9 by a mark on it with lower part shorter than the upper part. If the two parts subtend equal angles at a place on the ground, 15 m away from the base of the pole, what is the height of the pole?

• A. $60\sqrt 5 \,{\text{m}}$$
• B. ${\text{15}}\sqrt 5 \,{\text{m}}$$
• C. $15\sqrt 3 \,{\text{m}}$$
• D. ${\text{60}}\sqrt 3 \,{\text{m}}$$