Here's a worked question:

http://img249.imageshack.us/img249/5356/90726987.gif

Shouldn't the second to last line be:

$\displaystyle -3 \int^2_0 \int^3_0 \int^1_0 u^2 du dv dw$

where -3 is the Jacobian? Where did the $\displaystyle \frac{1}{3}$ come from?