a. Find the volume of a solid that lies between the planes perpendicular to the x-axis at x=0 and x=4. The cross-sections perpendicular to the axis on the interval are circular disks whose diameters run from y = x^^1/2 and y = -x^^1/2.

b. Find the volume using disk/washer method of the solid generated by revolving the region bounded by y = x^^1/2, x = 0, x = 4

(i) about the x-axis.

(ii) about the y-axis