what is the formula to use for this problem

Given answers are

#1: Arrival Rate = 1/50 = 0.02 calls hour.

#2: Service Rate= 1 hour (travel time) + 1.5 hour (repair time) =2.5 hours

With m = 1/ 2.5 = 0.4 hours per customers

a. .5380

b. .2972

c. 1-.2972 = .7593

d. 1.6082 hr

e. 4.1082 hr

f. .46.20

g. $275.27

OEI is satisfied that one service technician can handle the 10 existing customers. Use a waiting line model to determine the following information: (a) probability that no customers are in the system, (b) average number of customers in the waiting line, (c) average number of customers in the system, (d) average time a customer waits until the service technician arrives, (e) average time a customer waits until the machine is back in operation, (f) probability that a customer will have to wait more than one hour for the service technician to arrive, and (g) the total cost per hour for the service operation.

** I WOULD LIKE TO KNOW THE FORMULA TO USE **