The yellow area is 4 * 3 = 12 ft^2
The green area is a trapezoid
area = 1/2 (top + bottom) * height
= 1/2 (2+4) * 1
= 1/2 (6) * 1
= 3 ft^2
total area = yellow area + green area
= 12 + 6
= 18 ft^2
