Final answer:
To find the area of the shelf, multiply its width by its depth.
Step-by-step explanation:
To find the area of the shelf, we need to multiply its width by its depth.
The width of the shelf is given as 4 feet and the depth is not provided. If you have the depth value, you can simply multiply 4 by the depth to find the area of the shelf.
For example, if the depth is 2 feet, then the area would be 4 * 2 = 8 square feet.