Suppose processing times and the coefficients of variation of interarrival times and processing times are held constant. If utilization is increased from 80 percent to 90 percent, which of the following systems experiences the largest increase in the average waiting time in queue? 

a. A queue with 1 server. 

b. A queue with 10 servers. 

c. A queue with 100 servers. 

d. All of the above three queues experience the same increase.