How to integrate a function to find the volume:

Hello!

I've been pulling my hair out over this question, could you help me please?

the region between the curve y= (2x-1)^(-1) and the lines x=1 and x=b (where b>1) is rotated through 360 about the x axis

a) find,** in terms of b,** the volume of the solid generated.

b)show that, for large values of b, this volume is approximately pi/2

Ok so this what I've been doing for a)

http://img519.imageshack.us/img519/5567/calculus.png

while the actual answer for a is

http://img713.imageshack.us/img713/3...ulusanswer.png

so as you can see I am quite far off, I'd really appreciate it if you could explain how to get the right answer. You see I have either moved in the complete wrong direction or i just dont know how to get from the (ln) to the next level

Thank you!