Ok, this one is stumping me, I keep getting negative volume.

find the volume of the solid generated by revolving the region enclosed by the triangle with verticies (2,2) (2,4) (8,4) about the x-axis.

So I made a picture, found r(y)=2 and R(y)=y/3 (I did rise over run for the line, and solved in terms of y)

so i know its the integral

found my bounds, 2 to 4, did the algebra, found anti deriv. and evaluated on the bounds, but I got