Answer
240 square feet
Work Step by Step
This is a quadrilateral which has two parallel sides, therefore this is a trapezoid.
The area of the trapezoid can be calculated as:
$T=m\times \frac{a+c}{2}$, where m is the height and $a$ and $c$ are the parallel sides.
Here:
$T=10\times \frac{12+36}{2}=240$ square feet.