29,600 ft².
Here is how you find it:
First find the area of the piece of land, so multiply 140 feet by 220 feet. You should get 30,800 ft².
Next find the area of the building, so do 40 feet times 30 feet, and you should get 1,200 ft².
To find the remaining area, do 30,800-1,200. You should get 29,600 ft², the remaining area for the park.
Hope this helps!