Angles of elevation of pole are 60° and 45° from points at distances m and n on ground respectively. Here m, when measured from base of pole is less than n. What is the height of the pole?

• A. $\sqrt {mn\sqrt 3 } \,{\text{units}}$$
• B. $\sqrt {mn\root 4 \of 3 } \,{\text{units}}$$
• C. $\sqrt {3mn} \,{\text{units}}$$
• D. $\sqrt {mn} \,{\text{units}}$$