find the volume of a solid whose base is the semicircle $\displaystyle y=\sqrt{16-x^2}$ and whose cross-sections perpendicular to the x-axis are squares with the sides on the base.

ok I started of by graphing it then i get

Volume= $\displaystyle \int_{-4}^4 A(x) dx $

then after that I don't know what to do.

*edit**

I tried this numerous times and I think I got it. Tell me if this is the correct answer: $\displaystyle \frac{256}{3}$