Answer: 2, 4, 8
Explanation:
Assuming each box is equal to a factor 8 as the number of feet, there could be either 2, 4 or 8 boxes in the stack.
j = 1, 2, 4
The stack of boxes divided by j should equal a factor of 8.
I'm not sure however, so you might want to reconfirm if the question is complete.