A truck weighing station has a single scale. The time between truck arrivals at the station is exponentially distributed with a mean arrival rate of 1.5 vehicle/min. The time of taking vehicles to be weighted is exponentially distributed with a mean rate of 2 vehicle/min. When more than five trucks are in the system, the queue backs up onto the highway and interferes with through traffic. What is the probability that the number of trucks in the system will exceed five?

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