Evaluate $\int\!\!\int\!\!\int _{\mathcal{B}} f(x,y,z) \,dV$ for the specified function $f$ and $\mathcal{B}$:

$$f(x,y,z)=\frac{z}x\quad 2\le x\le 12,0\le y\le 3, 0\le z \le 8$$ $\int\!\!\int\!\!\int _{\mathcal{B}} f( x,y,z ) \,dV =$