Bill's Barbershop has two barbers available to cut customer's hair. Both barbers provide roughly the same experience and skill, but one is just a little bit slower than the other. The process flow below shows that all customers go through steps B1 and B2 and then can be served at either of the two barbers at step B3. The process ends for all customers at step B4. The numbers in parentheses indicate the minutes it takes that activity to process a customer. B3-a DM (12) B1 B2 B4 (9) (15) B3-b