ANSWER
72 cubic feet
Step-by-step explanation
The total volume of the box is the sum of the volumes of all the cubes that form it.
We can see that at the top there are 18 squares, which belong to the tops of 18 cubes. Also we can see that there are 4 rows of cubes along the height of the box. This means that in total there are:
72 cubes that form this box.
If each cube has a volume of 1 cubic foot, then the volume of the box is:
72 cubic feet.