single-server station

single-server station
Customers arrive at a single-server station in accordance with a Poisson process having rate λ. Each customer has a value. The successive values of customers are independent and come from a uniform distribution on (0, 1). The service time of a customer having value x is a random variable with mean 3 + 4x and variance 5.
(a) What is the average time a customer spends in the system?
(b) What is the average time a customer having value x spends in the system?
single-server station