Answer:
The average number of customers in a line = 2.25
Explanation:
We are given;
Mean arrival rate;a = 15 customers per hour
Mean service rate;s = 20 customers per hour
Now, we want to find the average number of customers in the line. It is given by the formula;
N_q = a(W_q) = a²/(s(s - a)
Plugging in relevant values, we have;
N_q = 15²/(20(20 - 15))
N_q = 225/100
N_q = 2.25