A small town with one hospital has two ambulances to supply ambulance service. Requests for ambulances during nonholiday weekends average .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. System utilization.
b. The average number of customers waiting.
c. The average time customers wait for an ambulance.
d. The probability that both ambulances will be busy when a call comes in.