A cylindrical drum $is$ being filled with oil while some $of$ the oils $is$ being drained. the radius $of$ the cylindrical drum $isr=1\mathrm{.}8ft.$ During the draining and filling process, the height $of$ the oil $in$ the drum $is$ modeled $byh(t)=8t-t^2,$ where $tis$ the number $of$ minutes after the process beings. $If$ filling and draining lasts for $8$ minutes, what $is$ the maximum volume $of$ oil $in$ the drum obtained?