(i)[3]
Find the area of the shaded region, showing all necessary working.
(ii)[4]
Find, showing all necessary working, the volume generated when the shaded region is turned through $360^\circ$ about the $x$-axis.
(iii)[5]
Find, showing all necessary working, the volume generated when the shaded region is turned through $360^\circ$ about the $y$-axis.