Approximating Area By Three Inscribed Rectangles

I'm working on a tricky problem. Hopefully I got it right.

If $\displaystyle \int_0^6 (x^2-2x+2) dx $is approximated by three inscribed rectangles of equal width on the x-axis. Determine the approximation of this integral.

After I graphed it, I found that the minimum is actually at 1. So the height of the first and second rectangles is 2. Therefore, their total area: $\displaystyle 2*2+2*2=8$.

The third rectangle's height: $\displaystyle 4^2-2*4+2=10. 10*2=20$.

Total area: $\displaystyle 20+8=28$.

Did I do it correctly? Hopefully I got this one right. Thanks everyone.