Trucks arrive at the receiving area of a distribution center at a Poisson rate of 10 per hour. The time required to unload a truck is exponentially distributed with a mean of 30 minutes. With 10 docks available for unloading trucks, what is the average number of trucks waiting to be unloaded? What is the average waiting time a truck spends? What is the average number of docks at which a truck is being unloaded?