In Exercises $13-26.$ calculate ${}_{S}f(x,y,z)dS$ for the ghen surface and fiunction.

$13.G(u,v)=(ucosv,$usinv,$u),0u1,0v1$; $f(x,y,z)=z(x^2+y^2)f(x,y,z)=\sqrt[\phantom{2}]{x^2+y^2}$

$15.y=9-z^2,0x3,0z3$;$,f(x,y,z)=z$

$16.y=9-z^2,0xz3$;$,f(x,y,z)=1$

$17.x^2+y^2+z^2=1,x,y,z0$;$f(x,y,z)=x^2.$

$18.z=4-x^2-y^2,0z3$;$,f(x,y,z)=\frac{x^2}{4-z}$

$19.x^2+y^2=4,0z4$;$,f(x,1,z)=e^{-z}$

$20.G(u,v)=(u,v^3,u+v),0u1,0v1$ :

$f(x,y,z)=y$

Part of the plane $x+y+z=1,$ where $x,y0$;

$f(x,y,z)=z$

Part of the plane $x+y+z=0$ contained in the cylinder $x^2+y^2=1$;$,f(x,y,z)=z^2$

$x^2+y^2+z^2=4,1z2$;

$f(x,y,z)=z^2(x^2+y^2+z^2{)}^{-1}$

$x^2+y^2+z^2=4,0y1$;$,f(x,y,z)=y$

Part of the surface $2=x^3,$ where $0x1,0y1$; $f(x,y.z)=z$ Do $25$