A population of 10 cargo aircraft each produces a profit of

A population of 10 cargo aircraft each produces a profit of $4,000 per 24-hour period
when not waiting to be unloaded. The time between arrivals is distributed exponentially
with a mean of 144 hours.The unloading time at the ramp is distributed exponentially with
a mean of 18 hours. It costs $150 per hour to lease a ramp with this unloading capacity.
How many ramps should be leased?

Solution