Question: The region R is bounded by the x-axis and the line and the curve with the equation where . Find in terms of the volume of the solid generated when R is rotated through one revolution about the x axis.

Here's what I've done:

(Integrating between the bounds 16 and 0 didn't know how to display that with latex)

After integrating I have

again for x= 16 and 0

solving that gives me the wrong answer

any ideas?