[SOLVED] Volume of a cylinder

I really dont know what im doing wrong. My online homework says this is wrong but im really sure its right :(

Can someone look this over for me. Thank you

The region bounded by http://webwork2.asu.edu/webwork2_fil...2c978940f1.png and http://webwork2.asu.edu/webwork2_fil...c777a8cb21.png is rotated about the line http://webwork2.asu.edu/webwork2_fil...2a969b3ca1.png.

Using cylindrical shells, set up an integral for the volume of the resulting solid.

Equation to use:

$\displaystyle

V = \int^a_b 2\pi r h dx $

r = right - left

h = top - bottom

i sketched the graph and this is what i get from it

r = 11 - x

h = 8x - x^2 - x ---> 7x - x^2

so my final volume formula will be

$\displaystyle

V = \int^7_0 2\pi (11-x)(7x-x^2) dx

$

I evaluate that and get

$\displaystyle

2\pi(428.75)

$

V = 2693.9157

Can anyone find anything wrong with this?

Thank you for any help :)