Customers arrive to the checkout area of Shoprite at the rate of $20$ customers per hour. The processing time for each customer is $9$ minutes on average. There are $8$ servers in the checkout area. What is the utilization rate $($in percentages$)$ of the servers? $($Note that your answer should NOT include $"\%".$ For instance, if your answer is $20\%,$ you should write $20$ in the blank$)$