Okay, after all the help ive gotten today i was able to do most of my homework. But one problem has me stumped.

A rectangle is formed by the points (2,0) (12,0) (2,2.6) and (12,2.6). This rectangle is revolved around the y-axis.

So I set up a washer problem whereby I say

(outside washer) INTEGRAL of: (pi)(r^2)dy

(inside washer) INTEGRAL of: (pi)(r^2)dy

r for the outside washer = 12

r for the inside washer = 2

INTEGRAL of: 144pi dy - INTEGRAL of 4pi dy

both evaluated from 0-2.6

And I get an answer of 1143.539726 but that is wrong.

What am i doing wrong? Not having an equation is messing me up.