In the parallelogram AECD, F is the midpoint of DC, so the areas of B and C are equal, and the sum of B and C is equal to the green area, that is, the green area is twice that of B, so the trapezoidal ABCD area is equivalent to the areas of five Bs, that is, the area of B is 100? 5=20 hectares, with a green area of 40 hectares.