From the base of a pole of height \( 20 \, \text{meter} \), the angle of elevation of the top of a tower is \( 60^\circ \). The pole subtends an angle \( 30^\circ \) at the top of the tower. Then the height of the tower is:
\( 15\sqrt{3} \)
\( 20\sqrt{3} \)
\( 20+10\sqrt{3} \)
\( 30 \)