A solid has, as its base, the circular region in the xy-plane bounded by the graph of x2 + y2 = 4. Find the volume of the solid if every cross section by a plane perpendicular to the x-axis is a quarter circle with one of its radii in the base.

I don't know how to go about this? Do I make it a definite integral? I'm not sure. What am I supposed to get here?