Customers arrive at a local 711 store at the rate of = 40 per hour (and

Customers arrive at a local 7–11 store at the rate of λ = 40 per hour (and follow a Poisson process). The only employee in the store can check them out at a rate of μ = 60 per hour (following an exponential distribution). Compute the following:
a) The percentage of time that the employee is busy with checkouts.
b) The average length of the queue.
c) The average number of customers in the system.
d) The average time spent waiting in the queue.
e) The average time in the system.