Answer:
400 ft²
Step-by-step explanation:
The maximum area of a rectangle results from it being a square. The rectangle (or square) must have 4 equal sides in order to maximize area. But in this case, one side is a wall. That means that the remaining three sides will be = 60 / 3 = 20 feet long. You formed an square that is 20 ft x 20 ft = 400 ft²