The Table Gives the Values of a Function Obtained from an Experiment

The table gives the values of a function obtained from an experiment. Use the values to estimate $\int _ { 0 } ^ { 6 } f ( w ) d w$ using three equal subintervals with left endpoints.
$\begin{array}{|c|c|c|c|c|c|c|c|}\hline w & 0 & 1 & 2 & 3 & 4 & 5 & 6 \\\hline f(w) & 9.7 & 9.1 & 7.7 & 6.1 & 4.2 & -6.6 & -10.3 \\\hline\end{array}$