8. Let $f(x, y, z) = \sqrt{x^2 + y^2 + z^2}$, evaluate the following surface integrals:
(a) $\iint_S f(x, y, z)dS$, where $S: z = \sqrt{x^2 + y^2}, x^2 + y^2 \le 4$. (**)
(b) $\iint_S f(x, y, z)dS$, where $S: z = \sqrt{x^2 + y^2}, (x - 1)^2 + y^2 \le 1$
9 Let $f(x, y, z) = x^2 + y^2 + z^2$ evaluate the following surface integrals