The answer is 40 boxes.
The reason for this is because 30 minutes Is half a hour. So you would multiply 4 boxes in 30 minutes by 2 to make it a full hour. So now we know he/she can do 8 boxes a hour. Now we have need to know how many boxes he can do in 5 hours. So we know they can do 8 boxes a hour. Then we will multiply the 8 boxes by 5 for the 5 hours. Then we get our answer of 40 boxes. I hope this help