Answer: The correct answer is c.
Explanation:
You take the area of the square which is 20x20 = 400. 
 
There is 5 squares 400x5 = 2000 
 
There is 4 triangles--which is 1/2 the area of 1 square (In this case). 
 
One triangle = 200 
 
200x4 = 800 
 
2000 + 800 = 2800