Using spherical coordinates, the integral \begin{equation*} \int_0^3 \int_0^{\sqrt{9-x^2}} \int_0^{\sqrt{x^2+y^2}} x \, dz \, dy \, dx = \end{equation*} a. $\int_0^{2\pi} \int_0^{\pi} \int_0^{3\csc\phi} \rho^3 \sin^2\phi \cos\theta \, d\rho \, d\phi \, d\theta$ b. $\int_0^{\pi/2} \int_0^{\pi/4} \int_0^{3\csc\phi} \rho^3 \sin^2\phi \cos\theta \, d\rho \, d\phi \, d\theta$ c. $\int_0^{\pi/2} \int_{\pi/4}^{\pi/2} \int_0^3 \rho^3 \sin^2\phi \cos\theta \, d\rho \, d\phi \, d\theta$ d. $\int_0^{\pi/2} \int_{\pi/4}^{\pi/2} \int_0^{3\csc\phi} \rho^3 \sin^2\phi \cos\theta \, d\rho \, d\phi \, d\theta$ e. $\int_0^{2\pi} \int_0^{\pi} \int_0^3 \rho^3 \sin^2\phi \cos\theta \, d\rho \, d\phi \, d\theta$
