Which of the following most directly expresses the motivation behind the expression “buffer or suffer”? 

a. Adding inventory to a process is likely to increase the flow time. 

b. To increase capacity, it is important to pool queues. 

c. If you want to increase the capacity of a process, add capacity first to the bottleneck. 

d. If there is variability in the arrival process or in processing times, make sure there is sufficient inventory between stages; otherwise, capacity will be reduced. 

e. Variability in the service process reduces capacity more than variability in the arrival process.