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.
I think its 1/2…hope this helps id it dont then.....:\¯\_(ツ)_/¯
The answer is b I hope this helps