Consider the region R bounded by the parabola y = 49 - x² and the x-axis. To find the volume of the solid when R is revolved around the y-axis, using the method of cylindrical shells:
a) Integrate from 0 to 7π.
b) Integrate from -7 to 7.
c) Integrate from 0 to 7.
d) Integrate from -7 to 0.