As shown in Fig.1, there are three point A, B and P on the even ground.
There are ABCD of a 3m-high rectangular wall and PQ of a 9m-high pillar standing on the ground straight.
Fig.2 shows the picture looked at these from right above.
Wall ABCD is illuminated by the electric light in the position at the tip Q of the pillar.
Find the area of the shadow of the wall made into the ground.
Neither the size of an electric light nor the thickness of a wall shall be considered.