From a point on the ground at distance of 3m from the foot of a vertical wall, a ball is thrown at an angle  ${\text{60}}^0$. The ball just clears the top of the wall and afterwards strikes the ground at a distance of 6m from the foot of the wall on the other side. The height of the wall is ____ (in m). $\left(\text{Take\hspace{0.17em}}\sqrt{\text{3}}\text{=1.73}\right)$