Please answer the question AND elaborately explain why you chose each of the formulas used and why is it a single or multiple server model or how do you know when a problem is one or the other? Please don't look at other's examples (copy and repost here).

For A&B: I'm confused because a previous Chegg example used Lq & Wq, but given my course, there were similar questions asking "How long does it take for a customer to get a ticket on average?" & "What is the probability that an arriving customer must wait for service?" And these were answered with system and not queue.

For C: I'm confused because a previous Chegg example also used Pw = Wq/Wa to solve this, but I learned the Pw equation as the probability that arrival will have to wait for service. What does it do with being busy? Can't you use the system utilization equation for this (p = arrival / M * service)?

Please answer this if you are confident. If answered these questions and explained clearly, will thumbs up!

A small town with one hospital has two ambulances to supply ambulance service. Requests for ambulances during non-holiday weekends average 0.45 per hour and tend to be Poisson distributed. Travel and assistance time averages two hours per call and follows an exponential distribution. Find: a. The average number of customers waiting for an ambulance. b. The average time customers wait for an ambulance. c. The probability that both ambulances will be busy when a call comes in