$$\text{a.}\;\;\;E = \bigg\lbrace (r, \theta, z)|0 \le \theta \le \pi/2, 0 \le r \le \sqrt{3}, 9-r^2 \le z \le 10-r(cos\theta + sen\theta)\bigg\rbrace$$ $$\text{b.}\;\;\;\int_0^{\pi/2}\int_0^{\sqrt{3}}\int_0^{10-r(cos\theta + sen\theta)} f(r, \theta, z)rdzdrd\theta$$