The vehicle count obtained in every $10$ minute interval of a traffic volume survey done in peak one hour is given below.

$$\begin{array}{|c|c|} \hline \text{Time Interval (in minutes)} & \text{Vehicle Count} \\ \hline 0 – 10 & 10 \\ \hline 10 – 20 & 11 \\ \hline 20 – 30 & 12 \\ \hline 30 – 40 & 15 \\ \hline 40 – 50 & 13 \\ \hline 50 – 60 & 11 \\ \hline \end{array}$$

The peak hour factor $\text{(PHF)}$ for $10$ minute sub-interval is ________________. *(round off to one decimal place)*