A rectangular package to be sent by a delivery service (see figure) has a combined length and

Question:

A rectangular package to be sent by a delivery service (see figure) has a combined length and girth (perimeter of a cross section) of 120 inches.

a) Use the diagram to write the volume V of the package as a function of x.
(b) Use a graphing utility to graph the function and approximate the dimensions of the package that yield a maximum volume.
(c) Find values of x such that V = 13,500. Which of these values is a physical impossibility in the construction of the package? Explain.