Oil leaked from a tank at a rate of $r(t)$ liters per hour. The rate decreased as time passed and values of the rate at 2-hour intervals are shown in the following table: $$\begin{array}{|c|c|c|c|c|c|c|}\hline \it{t \ (hr)} & 0 & 2 & 4 & 6 & 8 & 10 \\ \hline \it{r(t) \ (L/hr)} & 8.7 & 7.6 & 6.8 & 6.2 & 5.7 & 5.3 \\ \hline \end{array}$$ Find lower and upper estimates for the total amount of oil (in liters) that leaked out during these ten hours.

Lower estimate = liters

Upper estimate = liters