Consider the following dataset.

$$\begin{array}{|c|c|c|c|c|c|} \hline x & 1 & 3 & 5 & 15 & 25 \\ \hline f(x) & 6 & 8 & 10 & 12 & 5 \\ \hline \end{array}$$

The value of the integral $\int _1^{25} f(x) dx$ using Simpsonâ€™s $1/3$rd rule is ______ (round off to 1 decimal place)