The Port of Trop can service only one ship at a time. However, there is mooring space for three more ships. Trop is a favorite port of call, but, if no mooring space is available, the ships have to go to the Port of Poop. An average of seven ships arrive each week, according to a Poisson process. The Port of Trop has the capacity to handle an average of eight ships a week, with service times exponentially distributed. What is the expected number of ships waiting or in service at the Port of Trop?