A piece of cardboard that has a length of 9 feet and a width of 16 feet.
We are going to use this piece of cardboard to make an open top box by cutting equal size squares out of each corner and folding up the sides to construct the box.
a)Let X represents the side lengths of the square cut outs
sides reduced by x
16 feet becomes 16 - 2x
9 becomes 9-2x
volume , V of the cuboid or rectangular box
V=length x breadth x height
V = (16 - 2x)(9-2x)x = 4x^3 -50x^2+144x
b) The graph is attached with this answer
Maximum value of Volume at x=2
Length = 12, breadth = 5 and height = 2
Volume . V = 12 x 5 x 2 = 120 cube units
Dimensions are, 12,5 and 2