For a non-catalytic homogeneous reaction $A\rightarrow B$, the rate expression at $300\:K$ is $-r_{A}$$\left (mol\; m^{-3} s^{-1}\right )=\frac{10C_{A}}{1+5C_{A}}$, where $C_{A}$ is the concentration of $A$ (in $mol\;/m^{3}$). Theoretically, the upper limit for the magnitude of the reaction rate ($-r_{A}\:in\:mol\:m^{-3}s^{-1}$, rounded off to the first decimal place) at $300\:K$ is _________