Trucks arrive at a distribution center $($DC$)$ at an average rate of $10$ trucks per hour. Time studies revealed that, once trucks

have pulled up to a loading dock at the DC$,$ they can be unloaded at an average rate of $1$ truck per hour. Interarrival times

were found to be exponentially distributed, while effective unloading times have an associated CV of $0\mathrm{.}75.$

What is the minimum number of loading docks that the DC must have available to meet demand while maintaining the

utilization of each loading dock at less than $85\%$ to prevent major congestion?