Integration via shell method

Reviewing for my final and got one (of many) problems I keep getting a weird answer for. The problem reads:

Use the shell method to integrate. Find the volume generated by revolving the region bounded by the graphs of $\displaystyle y = \sqrt{x-1} $ and $\displaystyle y = x - 1$ about the line $\displaystyle x = 3$.

Using the shell method I set it up as $\displaystyle \int{(3 - x)(\sqrt{x - 1} - x - 1)$ from [1,2]. However, I get a negative volume. Any help would be greatly appreciated.

Thanks