Sharp Discounts Wholesale Club has two service desks (call them A and B) with one server at each desk. There is one desk at each entrance of the store. Customers arrive at each service desk at an average of one every six minutes following a Poisson distribution. The average service time at each service desk is 4 minutes per customer following the exponential service distribution.

a) How many customers, on average, are at service desk A waiting in line for service or being served?

b) How much time does a customer spend at service desk B waiting for help by the clerk?

c) Looking at service desk A, on average, what is the probability that there are at least three customers in line already waiting for service when the next individual arrives at this service desk?