The function $\mathrm{f}(x)=x^3-6 x^2+\mathrm{ax}+\mathrm{b}$ satisfies the conditions of Rolle's theorem in $[1,3]$. Then the values of $a$ and $b$ are respectively

$\mathrm{f}(x)=\frac{x}{2}+\frac{2}{x}, x \neq 0$ is strictly decreasing in

The rate of change of the volume of a sphere with respect to its surface area, when the radius is 5 m is

If the line $a x+b y+c=0$ is normal to the curve $x y=1$, then