If the perimeter is 39 what you have to do is 39 - 8.5 - 8.5 that will give you 22 and divide 22/2 and that gives you 11. So 11 is the length
Answer: The volume of largest rectangular box is 4.5 units.
Step-by-step explanation:
Since we have given that
Volume = 
with subject to 
So, let 
So, Volume becomes,

Partially derivative wrt x and y we get that

By solving these two equations, we get that

So, 
So, Volume of largest rectangular box would be

Hence, the volume of largest rectangular box is 4.5 units.
The answer to this is 720000

Question 11 :
the equations are :
now, let's graph the lines ~
As you can see in the attachment, The lines coincides each other, so the equations are :