A box with an open top is to be constructed from a square piece of cardboard, 3 ft wide, by cutting out a square from each of the four corners and bending up the sides. Find the largest volume that such a box can have. Let x denote the length of the side of the square being cut out. Let y denote the length of the base.
a) Write an expression for the volume V in terms of both x and y.
b) Use the given information to write an equation that relates the variables.
c) Use part (b) to write the volume as a function of only x.
d) Finish solving the problem by finding the largest volume that such a box can have.