A $\text{PD}$ controller with transfer function $G_{c}$ is used to stabilize an open-loop unstable process with transfer function $G_{p}$, where
\[
G_{c}=K_{c} \frac{\tau_{D} s+1}{\left(\frac{\tau_{D}}{20}\right) s+1}, G_{p}=\frac{1}{(s-1)(10 s+1)}
\]
and time is in minutes. From the necessary conditions for closed-loop stability, the maximum feasible value of $\tau_{D}$, in minutes, rounded off to $1$ decimal place, is $\_\_\_\_\_\_\_\_$