$$\text{a.}\;\;\;E = \bigg\lbrace (r, \theta, z)|0 \le r \le 3, 0 \le \theta \le \pi/2, 0 \le z \le rcos\theta + 3\bigg\rbrace$$ $$f(r, \theta, z) = \frac{1}{rcos\theta + 3}$$ $$\text{b.}\;\;\;\int_0^3\int_0^{\pi/2}\int_0^{r(cos\theta + 3)} f(r, \theta, z)dzd\theta dr = \frac{9\pi}{4}$$