Hey there!
The correct answer is 40 units squared.
We can solve this by breaking up the shape. There are four equivalent right triangles, so we can solve for one, and multiply it by 4! The area of a triangle is bh/2 or base * height / 2. So, we can set up the following equation:
(4 * 5) / 2 = area
20 / 2 = area
10 = area
Now we can multiply it by 4, which gives us 10 * 4 or 40.
Have a terrificly amazing day! :D