A region in the xy-plane is bounded above by the graph of y=4−x2 and below by the x-axis. The region is revolved about the x-axis to create a solid of revolution. Which of the following integrals gives the volume of the solid?
a) ∫02π(4−x2)2dx
b) ∫−22π(4−x2)2dx
c) ∫−22πx2dx
d) ∫−22π(4−x2)dx