Szukana fraza: [Abstract = "A multi\-server queueing system with two types of customers and an infinite buffer operating in a random environment as a model of a contact center is investigated. The arrival flow of customers is described by a marked Markovian arrival process. Type 1 customers have a non\-preemptive priority over type 2 customers and can leave the buffer due to a lack of service. The service times of different type customers have a phase\-type distribution with different parameters."]