Could someone please help me with this problem?

Calculate the integral

$\displaystyle I = \int {\int\limits_D { \int {xdxdydz} } }$

where D is the region in R3 given by the inequalities $\displaystyle x^2+y^2+z^2<=1$ and $\displaystyle -x<=y<=\sqrt{3}x$

How do you deal with that last inequality?