Can you please help with the following exercise:

At the order fulfillment center of a major mail-order firm, customer orders, already packaged for shipment, arrive at the sorting machine to be sorted for loading onto the appropriate truck for the parcel's address. The arrival rate at the sorting machine is at the rate of 100 per hour following a Poisson distribution. The machine sorts on average at the rate of 125 per hour and exponentially distributed.

(a) What is the average number of packages waiting to be sorted?

(b) What is the average number of packages in the sorting system?

(c)How long must the average package wait until it gets sorted?

(d) What would Lq and Wq be if the service rate were constant, not exponential?