4. Use the Disk/Washer Method to find the volume of the solid generated by revolving the region bounded by $y = \sqrt{x}$, and the lines $y = 2$ and $x = 0$ about
a) the x-axis.
b) the y-axis.
c) the line $y = 2$.
d) the line $x = 4$.
5. Use the Disk/Washer Method to find the volume of the solid generated by revolving the region bounded by $y = x^2$ and the line $y = 1$ about
a) the line $y = 1$.
b) the line $y = 2$.
c) the line $y = -1$.
6. Use the Disk/Washer Method to find the volume of the solid generated by revolving the region bounded by $y = \ln x$, $y = 0$, and $x = e$ about the x-axis.